Atlantis I
Level built by Baddy.
Walkthrough written by Jose Boo.

Initial comments:
This is a good level with which you can pass a good time playing.
The rooms are not too much big, the geometry is well, the textures are good and the enemies are well made.
The lights are not very good and I haven't found some flares in all the level (bad, bad, ...).
There are many few pickups, and no guns and ammo (only the desert eagle).
I haven't found any secret too.
Although this, the level is very playable, and I recommend to play all Tomb Raider players. I have much fun. (Thanks Baddy)
This walkthrough is only if you get stuck you can finish the level. I don't put all the pickups (some small medipacks) only those that are necessary to continue playing and finish the level.

Walkthrough:
First observe the initial cut-scene. The level begins when Lara leaves the mini-submarine near of the subacuatic ruins of Atlantis.

A shark attacks. Go west till you find a yellow subacuatic cave. Go into that cave and you'll find two submarinists shooting you. Go out of the water (they can't do it) and kill them and the shark too. One of them lets the desert eagle and another one the lasersight. Combine both things and shoot the bell over the door. The door opens.

Enter and beware with the rocks that fall to the ceiling. When you approach, one of the shiva statues takes life and will attack you. Kill it. Near where the statue was go over a block and do a single jump over the spikes and grab the nearest block to the left. Continue jumping-sliding-grabbing over the blocks around the wall till get into a opening in the east wall near the bell of the entrance. Go in and press action to move the vase over the pedestal. This raises a block near the entrance. Use it to get a high opening at the NE side of the room.

Enter the small room and activate a wall-switch at the center of the north wall. This opens the next door below. Go down and enter that door.

Enter and notice the little opening in the west wall between the statues. You can see a key (use the binoculars) you'll get soon.

Go east and jump into the water, turn left at the end and go back if you want kill the shark. Enter in a large underwater zone. Swim high and find a little opening behind a plant high in the west wall, entering at another underwater zone. Go down now and swim into an opening in the SW corner. Follow the path a little (not till the end) and behind a pillar to the left you'll find the place where you saw the key before. Go surface and pick up the key.

Go back to the first large subacuatic area an enter into a crack in the north wall. There are two doors. Go to the east door and use your key.
Go ahead and to the right till the end. Some tiles break in the floor when you walk over them and you can swim into a new water room.
Go south and find an opening up in the SE corner. Go out of the water and enter into a new room. A fly-by show you the tiles you have to jump over if you want survive (the room is full of hidden spikes). So, jump only over that tiles: earth-fire-air-water and get the other side of the room safety. Here, make your way to go up to the upper ledges (you can situate below the opening to the left and press "action + forward" standing at the most right side or otherwise jumping backwards to the slope to your right to jump and grab the tallest pillar).

Here up, there is a moveable block in the SW corner of the ledge. Pull it out and aside to enter a little room with breakable tiles on the floor. Walk over them and fall down (beware with the spikes).
Go west and into a new room with columns where you can find the second key in the NW corner of this room. Pick it up.

There are two ways to go back to the begining of the level: the normal way is go to the dark SE corner of the room and behind the column you can jump and get the crawlspace to drop down to the other side of the wall; but there is another way most simply: go down the stairs and into the obstructed opening down, standing in front of the rock, press "action + forward" and Lara will climb over it to the other side. The controls working so ! (Could be this a bug?)
Well, make your way to go back to the room where the two doors were and use the new key to open the second door (in that way, another statue takes life and attacks Lara). Go in and at the end of the path find a large room with spikes on the floor and pillars with swinging bags over them. It's a bit tricky to get the other far side of this room, I got it this way:

Save your game first! Do a running jump and grab the edge of the first pillar; shimmy right till the corner (not go the other side) and when the bag is at the most right position, press up and do a second rumming jump to get the edge of the second pillar; again, shimmy right till the most right side of the edge and when the bag is at the most right position, press up and don't slide down the slope, standing at the higest point of the pillar, simply do a standing jump to grab the edge of the third pillar. Here, you can shimmy left or right around two corners to get the other side of the pillar, stand up safety and save your game with tranquility. The most difficult part had been passed. From here, do a standing jump to grab the edge of the fourth pillar and again shimmy left or right around two corners to get the other side of the pillar and stand up; another standing jump to grab the edge of the last pillar again shimmy right and when the bag is at the most right position, press up and now you can slide down the slope and jump finally into the open. Uf!

Enter in a new room and go south through the obstructed corridor till the rocks which don't let you go more long. Turn left and notice a crawlspace down in the east wall (light a flare if you need). Put Lara as next as you can, press action and Lara will open the crawlspace with your feet. Enter and get a PINK CRYSTAL at the end behind a pillars. Get back to the room with the statues. Beware with the falling rocks of the ceiling.
Go towards the door and approach to the statue of the right side. The statue wakes up and attacks Lara. Kill it and behind where the statue was, a block has raised and you'll find a wall switch that makes wake up another statue. Continue killing statues and activating wall switches behind them till you kill the last in the west wall and that last switch opens the large doors. Go in.
Go along the corridor, pass the water and go till the end at the other side. Climb the block and pull the last wall switch (light a flare if you need) that opens an underwater door outside. Jump in the water and go through the opening to an underwater zone. Swim till the three columns are and get there the second PINK CRYSTAL. Then go west and swim trough the doors you have opened moments ago.
Go out of the water and use the crystals in the serpent's mouths to open the last door and be prepared for the final battle. Go to the SW corner to pick up some ammo for the desert eagle and shoot the monster till he dies and lets a blue hand. Picking up that hand the level finishes with another cut-scene.

Jose.