Note: I have refrained from giving compass directions, as East and West are flipped in this level for some reason. Accounting for it would have made the walkthrough cumbersome to write and read, and liable to cause confusion; and the compass isn’t easy to read here anyway.
If you want all secrets but missed one somewhere down the line, you can go back for it at any point; by the end the entire level will have opened up.
You begin the level in the locker room of an underwater base. Pick up
Standard Bolts (for the harpoon gun) in an alcove in your back and, in the next room, a big medipack floating a bit above one of the tables. Drop down into the pit with the pipe to get a view of an area you will be entering shortly. Clicking the switch near the pipe opens the door ahead, and also causes agitation in a frogman. Note the harpoon gun lying on the floor in that area, highlighted by the camera view.
Go through the door into a corridor. On your left is a door you can’t open from here, so turn right, drop into another pit and pick up a small medipack and Poisoned Bolts. The harpoon gun waiting for you in the adjoining area is highlighted again. Go through the doorway into an octagonal room. The door straight ahead requires a key which you don’t have yet. Use the valve switch on the wall to your left, opening the door in your back.
This door doesn’t lead directly to the room where you can pick up the harpoon gun, but to an adjoining room in which two frogmen are waiting on high alert. If you’re the adventurous kind, you can jump straight into the water and make a quick dive past the frogmen to the room with the harpoon gun; alternatively, step carefully through the door onto the slightly sloped block immediately behind it and kill the frogmen from there with your pistols. (The railing around the platform ahead prevents you from hitting the frogmen, but it doesn’t prevent them from hitting you, so better stay on the slope. You will have to step briefly onto the platform to make the second one jump into the water, though. You can’t harm them while they’re on dry land.)
When the frogmen are dead and gone, jump into the water and search the room for two shotgun ammo pickups (one of them wideshot). Diving through the opening in the floor, you can also collect 3x Standard Bolts and 1x Poisoned Bolts from recesses in the walls (mind your air meter, as the surface is now some way away), but both of the two opposing arched doorways down here lead at present only to dead ends at closed doors.
The secret you can acquire at this point is described in the section regarding the Diving Supplies Room Access Plug, when you need to go that way anyway.
Back in the upper room where the frogmen were, pass through the yellow arched doorway, go up and climb out of the water into the room where you can pick up the Harpoon Gun along with another set of Standard Bolts.
Turn around and climb the ledge behind two tables in the opposite wall. The room behind it contains a number of pushable cages. Pull the first one once and push it into the alcove. Push the second one twice. (Don’t bother about the others, as they are obviously not meant to be moved.) This grants you access to a closed door on your left and a doorway on your right. The latter leads to a small room with a grated wall overlooking a room in which a blue rock pillar rises out of the water.
On your left, there’s a valve switch which opens the door back in the room with the pushable cages; on your right, an empty socket for a yellow plug; and on the floor, an administrative notice (use the cursor keys to rotate) informing employees that the Diving Supplies Access Plug has gone missing (that’s the plug that goes into the socket on your right). The “Diving Tips” on the reverse recommend that divers bring along an aqualung as well as poison harpoons (“effective against sharks”) and explosive harpoons (to be used with caution, as they may damage submersibles operated by other employees).
Turn back and go to the door opened by the valve switch. Behind it is a tiny room built for the sole purpose of containing a pushable cage for you to shove into the water of the room beyond, which is the room in which you previously killed two frogmen. Another one has appeared in the meantime, so kill him too. The cage you shoved into the water provides you with a makeshift ledge that you can use to climb out of the water and, more importantly, to jump over to the higher ledge that you couldn’t reach before.
On that ledge is a small medipack and another valve switch, this one opening a gate in your back. In the cramped and half-submerged room behind it, pick up the Central Diving Area Access Key. It goes into the only keyhole you’ve come across, the one in the octagonal room you’ve passed through shortly after the start of the level. Use the cage in the water to jump across the railings, go through the opening straight ahead and use your newly acquired key.
As you pass through the door into the new area, a wrench-wielding worker comes charging at you. When he’s dead, familiarise yourself with the surroundings, as you will be spending quite a bit of time here.
You are in a wide corridor with lots of crates arranged in such a way as to give it the appearance of an obstacle course; and indeed, the timed switch in an alcove at the far end of the corridor will turn it into just that. Don’t use that switch yet, though, as you have to get a number of other obstacles out of the way before you can complete the timed run and eventually enter the underwater area of which you get a panoramic view through a succession of windows on the right-hand side of the corridor.
The first point of interest on the left-hand side is a crawlspace above a slanted block; its other end is blocked by a grate. (Ignore it if you’re not after secrets.) Next up is a recreational bay, where you can collect flares, a small medipack and the shotgun from the various tables. It overlooks a largeish water area with a crane and three frogmen, who are at present engaged in performing a silent water ballet (again, a railing prevents Lara from actually hitting them); beyond lies what looks to be another corridor stacked with crates, with an armed guard moving about in a somewhat agitated manner.
The next bay on the left provides a ramp for you to go down into the area you’ve just seen from above. Somewhere around here another aggressive worker is triggered in your back; he leaves behind a big medipack. Then follows the alcove with the timed switch mentioned above.
When you’re ready, go down the ramp with weapons drawn. Don’t mind the armed guard up above (he seems to quietly withdraw so as to not get involved in any violent proceedings) and concentrate on the aquatic menace instead. Killing the second worker may have disturbed the water ballet and dispersed the frogmen, with unpredictable consequences: some or other may have become stuck in an underwater ceiling tile (rendering them unkillable, but also harmless); in one instance, I encountered one floating through the air.
When you’ve killed all three (or when they’ve incapacitated themselves, as the case may be), jump into the water and use the underwater switch on the wall underneath the crane. It opens a door far, far away, back near the beginning of the level. You will pass through it during the upcoming timed run.
Get out of the water and face the row of four valve switches. You need to use these to turn off four burners, also part of preparing your path for the timed run. Four switches for four burners, you say? Yes, but this is Tomb Raider, man…so of course it’s not like there’s one switch for one burner. The quickest solution is this: use only the first and the fourth switch, counting from either left or right, and ignore the two in the middle.
There is still one final door to open before you can do the timed run. Go back up into the corridor with the crates and turn right and right again to backtrack near the beginning of the level. Go through the door at the far end of the long corridor (this is the one opened by the underwater switch) and draw your guns as you enter the other corridor full of crates that you’ve previously seen from across the water. It turns out that the guard here isn’t averse to violence after all, he just went to bring back one of his buddies.
Kill them both, then open the floor trapdoor next to the first stack of crates, drop down and pick up the Poisoned Bolts on top of another crate. At the other end of the room are three more crates which are unobtrusively marked as pushables. Of these, pull and push the first one on your right under the ceiling trapdoor, then use the valve switch that was hidden behind it to open the last door before the burners. Ignore the other pushables and exit through the ceiling trapdoor.
Everything is ready now for the extended timed run all around the room with the crane, but don’t do it just yet. Go through the door that leads to the burners and use the switch at the far end of the corridor to do another one instead. This one is tight but short (think of it as limbering up for the big one): use the switch, press the Look key to make the camera go away, roll, jump over the railing, get in the water and pass through the trapdoor as it closes. (I found that landing on the slope below the railing and jumping in the water from there doesn’t help you save time, but this way you can avoid the health loss incurred by landing on the flat ledge, if that is a concern of yours.)
Kill the two frogmen and collect flares, shotgun ammo, Standard Bolts and the Underwater Cave Access Plug that lies on top of the pillar (it’s blue, so it won’t fit in the yellow receptacle you’ve seen, but you’re going to need it shortly).
If you’re going for secrets and/or are a fan of timed runs, you can do another one straightaway. Pass through the one-click crevice in one of the diamond-shaped yellow recesses, pull the underwater switch at the end of the tunnel, press the Look key to make the camera go away, roll and go back through the tunnel, up through the trapdoor and out of the water, then run up the ramp, turn right and run/jump to the crawlspace (mind that you need to press the Duck key to enter). When you made it, immediately crawl forward or else the door may still push you out as it closes. This secret (1/4) rewards you with 3x Explosive Bolts. When exiting, avoid the water cooler below the crawlspace, as colliding with it will beam Lara back up into the crawlspace.
Now’s the time for the big one. Go to the end of the corridor with crates and use the switch in the alcove. This timed run is long and tight and can therefore easily be frustrating. There are no clever shortcuts for you to take, though you can tackle the subsidiary tasks in a number of ways: for example, I would usually try to jump on top of the high crate next to the alcove and continue with a running jump from there, but you can also run/sprint around the first batch of crates, and (hopefully) make it in time either way. (If you bump into any of the crates right at the start, however, you might as well abort the attempt and start over.) Save repeatedly at opportune moments (e. g. mid-jump) if you think you’ve given it your best during a particular section, and use different slots to do so.
As soon as you’ve made it, draw your guns, as you will be immediately attacked by another wrench-wielding worker (leaves a small medipack). There are Standard Bolts on the floor in front of the yellow door. Go through the open door at the far end of the corridor and enter the sleeping quarters. As you pass by the door at the other end of the room, another worker emerges. This one carries a personal note in which he confesses to have lost an unnamed thing related to the Diving Supplies Room, possibly near “the top of the yellow bell” in “that big underwater cave.”
Return to the corridor and climb up to the crawlspace opposite the yellow door. You emerge on a ledge at the top of the room with the crane. Use the grated ceiling to monkeyswing across the gap to another ledge and use your Underwater Cave Access Plug there.
A flyby shows you the route you’re now supposed to take. A frogman will be waiting for you in the room where you dropped the pushable cage into the water. Dive to the bottom of that room and enter the tunnel shown in the flyby. You can pick up 2x Standard Bolts along the way here.
Beyond the triangular hole in the ceiling lies the underwater cave you’ve previously seen through the panoramic windows, so you know that three hammerhead sharks will be waiting for you there.
When you’ve killed them, take a breather in the air pocket in the middle of the ceiling. You can get Standard Bolts and a big medipack from alcoves in the yellow wall, but there are no other pickups to be found, specifically nothing to do with diving supplies. This is because it turns out that this is not the “big underwater cave” mentioned in the worker’s note, nor is the diving bell the one referred to there.
What you need to do now is find three underwater levers to open the gate at the far end of the cave. Two are near the ceiling, at the opposite ends of the cave; the third is near the bottom, mounted on the back of one of the yellow metal pillars. Make sure that your air meter is full before you pass through the gate.
There are three more hammerheads around, plus two submersibles that launch rockets at you when they get the chance. It’s best to simply ignore them for now; if you make a beeline for the bottom of the large central structure straightaway, they won’t bother you too much, or indeed at all.
Inside the central structure, Lara wonders what might be “up there,” i.e. on top of it. Before you satisfy her curiosity, pick up 2x Standard Bolts, flares and a small medipack on the ledges, and take note of the four empty sockets (2x blue, 2x yellow) on the pillars.
Use the opportunity for assessing the lay of the land, then plop back into the water and swim up to the top of the structure to pick up the Diving Supplies Room Access Plug. A cutaway camera confirms that, yes, you’re supposed to backtrack now.
So, go all the way back to the room where you pushed the cage into the water, climb up onto that cage, re-enter the cramped interior with the other pushable cages and find the receptacle where you can insert your yellow plug. A camera shows a gate opening next door. Leave the way you came, get back in the water, dive to the bottom, and this time enter the tunnel opposite the one that leads to the underwater cave.
When you exit the tunnel, turn immediately right and spot a camouflaged one-click crevice at the bottom of the wall. Inside is a secret (2/4), 3x Poisoned Bolts.
You emerge in the room with a tall blue pillar in the middle which you’ve seen before from the other side of the grate. “I could probably grab that grated wall,” muses Lara as she gets out on a one-tile ledge. Follow her suggestion and take a running jump-grab with a curve to grab the grate, move right to the third and last segment of the grated wall, climb up and backflip-with-twist to grab the edge of the pillar in your back. Pull up and jump the gap.
A worker will attack you in a narrow corridor. Ahead in another narrow corridor lies a big medipack on the floor; as you pick it up, another worker comes up from behind. Turn into the room with the grated wall and grab the Aqua Lung from the table, as well as the Poisoned Bolts and Explosive Bolts on the floor. (This Aqua Lung is a miraculous new device that doesn’t need to be connected to any oxygen tanks, and it’s sufficient to simply carry it in your pocket. From now on, you have unlimited air whenever you are submerged in water.)
Now return to the large underwater cave. If you haven’t killed them before, some or all of the hammerheads may have followed you into the cave where you previously used the three underwater levers. The submersibles on the other hand have a tendency to get stuck in the walls, thereby incapacitating themselves like the frogmen in the room with the crane; if they haven’t done that, use your explosives to get rid of them.
Note: Several tasks in this area can be completed in any order. For the purposes of this walkthrough, I’m going to start at the entrance and work my way around the cave clockwise from there. The following paragraphs are numbered for ease of reference. Strewn about the floor of the cave are some Standard Bolts pickups which I’m not going to enumerate here.
§ 1 Immediately behind the entrance, dive up to the ceiling and find an underwater lever mounted on a yellow metal plate. As shown by a cutaway camera, it opens the right-hand door in a group of three located elsewhere.
§ 2 Continue along the left wall towards the walkway that connects a closed gate to the central structure. Above it is an opening with the three doors you just saw in a camera view. Pull the one underwater lever that is accessible at this point. A cutaway camera shows another door opening somewhere at the bottom of the cave.
§ 3 Leave this alcove and turn left. Go past the central structure and find an opening in a brown wall (“Tinnos” textures) at ground level. This is at the far end of the cave, opposite the entrance. Inside is an enclosed corridor that you can’t enter right now, as four consecutive doors are blocking your way; but you can pick up flares and a small medipack here.
§ 4 Turn back and dive towards the central structure; when you reach it, go straight up and find another opening near the ceiling. This one contains a set of four underwater levers; obviously it’s a variant of the valve switch / burner puzzle. This time, ignore the first and last ones, and use only the ones in the middle (#2 and #3) in order to open all the doors in the enclosed corridor you’ve just come across.
§ 5 Go back out and return to opening in the wall you’ve visited under § 3. At the end of the enclosed corridor, pick up your first Blue Circuit Plug (1/2).
§ 6 Go back out, turn left, and continue along the cave wall. Near the ceiling, behind a jellyfish, is an alcove with Standard Bolts.
At the end of this alcove is a camouflaged one-click crevice, and behind it a short tunnel with an underwater lever that opens a yellow door in some place you haven’t been to yet. This is required for accessing a secret (see below).
Go back out of the alcove and dive straight to the bottom. Nearby are two openings positioned at right angles to each other. The one on the right is blocked by a grate, but the door on the left should be open (underwater lever, § 2). Pick up 2x Standard Bolts as you pass through and follow the tunnel until you reach an intersection.
The yellow door ahead is open if you’ve pulled the underwater lever behind the camouflaged crevice mentioned above. Enter to collect your secret pickups (3/4): a big medipack, Explosive Bolts and 2x Standard Bolts. Return to the intersection.
Turn to enter the next tunnel; then go right if you want more Standard Bolts, otherwise go left and follow through until you reach an area with pillars and pipes and a large air pocket overhead. Straight ahead on the floor is a flare pickup, further on and to the right a big medipack; there are also 2x Standard Bolts elsewhere on the floor. At one end of this cave, you can climb out of the water towards a switch on the wall. It turns off the fires on the pillars, but of course only for a short while.
Flip the switch, roll and take a running jump-grab with a slight left curve. If you made it, save while Lara pulls up. Now take a running jump without grab to the next pillar; aim for the right-hand side of the top of that pillar, so you don’t waste too much time lining up the next jump. This next jump is a running jump with grab again. Run across the top of the last pillar and jump to the yellow metal structure ahead. When you turn the valve switch, you get a camera view of the diving bell back in the large underwater cave rising and revealing a Yellow Circuit Plug.
§ 7 Leave this cave the way you came. As you re-emerge in the large underwater cave, ahead and to the right you can spot another underwater lever mounted on one of the legs on which the central structure rests. Pulling this lever opens the door at the centre of the group of three doors which you’ve encountered under § 2. Ignore this for now, we’ll return there in due time.
§ 8 Continue with the cave wall on your left until you reach the place where the risen diving bell (§ 6) revealed a Yellow Circuit Plug (1/2). A little further ahead and near the ceiling is a largeish metal construction in the wall with an opening that is blocked by a 2-click grate.
§ 9 Continuing further with the wall on your left, you’ll encounter another underwater lever mounted on a metal panel at floor level. It opens the left one of the three doors you’ve encountered under § 2.
If you dive straight up now, you can spot the second Blue Circuit Plug behind a grate in the wall near the ceiling, as well as the second Yellow Circuit Plug behind a similar grate a little further to the right of the former, but of course you can’t reach either from here.
In between these grates near the ceiling and the underwater switch at the bottom below, there is a slanted crevice in the cave wall, close to the top of the vaguely cylindrical yellow metal structure, which appears to have been cut off from the central structure by some accident. Following the tunnel behind this crevice and going up a shaft, you can pick up Standard Bolts and a small medipack, but the door in here is closed at this point.
§ 10 We’ve come full circle now. Return to the opening above the walkway connecting a closed gate with the central structure. The three doors in here should all be open now if you’ve used the relevant underwater levers mentioned in §§ 1, 7 and 9.
You’ve used the underwater lever on the right already in § 2. The one on the left opens the two-click grate near the risen diving bell (§ 8); the one at the centre opens the door you’ve come across after entering the slanted crevice (§ 9). Return to these places in whichever order you prefer to collect the remaining Blue Circuit Plug (2/2) and Yellow Circuit Plug (2/2). You are not asked to perform any additional tasks while doing so, though you can pick up more Standard Bolts along with the blue plug.
With the four plugs collected, return to the central structure and place them in their receptacles. This opens the gate at the end of the walkway, which leads to the Research Laboratory.
First, though, you have to negotiate another underwater cave, into which the Research Laboratory has been built. As you enter, you are accosted by a mutant fish. Two more of its kind are waiting for closed gates to open, and there are several nooks and crannies sprinkled throughout this cave in which more closed doors or trapdoors are hidden.
To get going, swim past the diving bell into another section of the cave, at the end of which is an enclosed walkway in which an agitated worker runs back and forth. Dive up close to this walkway and turn around. Ahead and near the ceiling is a wide opening (sort of a first floor above the ground floor), and to the right of it and a little higher is a small triangular one behind which you’ll find an underwater lever mounted on a yellow metal wall. A cutaway camera shows a yellow door opening in a narrow tunnel elsewhere.
Turn around and swim back towards the entrance. The narrow tunnel you’ve just been shown is cleverly hidden at the ceiling close to the last of the three jellyfish which are hovering in this part of the cave. Beyond the tunnel and the yellow door, pull out of the water and enter a crawlspace. Grab the small medipack on your right and follow the crawlspace to an opening in the floor.
Safety-drop down onto a stack of crates. (All the crates in this stack and the next are pushables, but you can’t move them, nor are you meant to.) If you desire more Standard Bolts, there are some in an alcove near the crates. There are two doors with valve switches that won’t respond to your exertions, and a short corridor which leads to a room with a cage in the middle and two receptacles for Mutant Probes at the far end. This is where you get to be shocked by the results of the dastardly experiments that are being conducted, but with you being two Mutant Probes short, there’s nothing else to do here just yet.
Back in the room with the crate stacks, draw the attention of the guard next door. He’s rather lenient towards intruders as long as they go about their business quietly, so draw your pistols and fire off a few rounds. Eventually the guard will storm in to tell you off. Kill him and enter the room where he came from. The ground floor holds nothing of interest, except a note on the table in the middle of the room (which has, however, no bearing on gameplay), 2x Normal Bolts at the end of the corridor that runs along the panoramic windows, and a small medipack on the floor next to a fan.
The corridor in between that fan and some more floating mutant corpses goes up to the floor above. There’s a recreational area here (no goodies on the tables this time), a closed door that leads to the enclosed walkway with the worker you’ve seen before, and three more pushable crates. Unlike the others back on the ground floor, these can be moved, but there’s nothing behind or beneath them.
Spot the valve switch in an alcove opposite the ledge near the crates and take a running jump-grab there. The switch opens one of the doors in the cave outside, behind which a mutant fish was waiting for this to happen. Jump back to ledge where you came from.
For a secret (4/4), shove one of the crates off the ledge anyway. The quickest way is a running jump across the railing from a corner of the recreational area. When you land behind the first crate, push it in the direction of the valve switch and off the ledge, then drop down to the floor and push it far enough for you to reach a second alcove with another valve switch above. Turning this switch opens the other door back in the room with the stacked crates where you first entered this area. Behind that door are sleeping quarters in which some workers are sleeping it off, in full gear and clutching their beloved tools. Their sleep is so deep that you can’t wake them no matter what you do, but two more are spawned in different spots as you scour the area, picking up 3x Normal Bolts. The closed door opens when you approach it from the aisle in the middle, and out comes Sophia Leigh, suffering from a hiccup and maybe a more serious condition (don’t need explosives). In the loo she emerged from is a big medipack and 3x shotgun ammo (2x red, 1x blue).
Back in the recreational area, climb the pillar on top of which you can spot a switch. The door to the enclosed walkway opens, and finally freed, the worker emerges; kill the ungrateful sod (or ignore him if he just walks away: this happened to me on one occasion, and I couldn’t find him anywhere afterwards. He’s also prone to running into walls). Enter the walkway (if you do it with guns drawn, Lara may target an object that only she can see). The yellow door at the far end requires a key; the valve switch opens a trapdoor somewhere in the cave outside.
Return to the recreational area. Climb on top of the other pillar and pull up into a short tunnel. Push the crate at the end of it once to open up an exit leading back to the underwater cave (you may have noticed that you can’t leave the laboratory any other way). Drop down into the water, dispatch the mutant fish that’s been waiting for you, and collect your first Mutant Sample (1/2) in the tunnel above the diving bell.
Turn left as you leave the tunnel and swim past the enclosed walkway up to the trapdoor in an opening behind it. Pull the underwater switch to open the gate to another underwater tunnel with a mutant fish. Leave the tunnel, dive down and turn right, kill the mutant fish and pick up the second Mutant Sample (2/2).
Backtrack through the trapdoor to the room where the receptacles for the Mutant Samples are. When you have inserted both, an explosion occurs, and the mutant in the cage (who had apparently been sleeping) is freed, awakes and goes after you. (I recommend the shotgun.) It turns out that the mutant holds the Key to Surface. Pick it up, backtrack to the enclosed walkway upstairs and use the key on the keyhole next to the yellow door. Drop down into the water and, after an uneventful swim through an underwater tunnel, climb out and go up to the rubber boat to end the level.