Jump from the ledge over to the ladder and press the button in the hall to stop the deadly fan. Now you can safely dive in and get the grenades beneath the fan. Now go flip the switch near the walkway to open the sealed door and continue down the hall. A Doberman and two guards attack from the left so finish them off before continuing. Get the shells and Uzi's if needed then use the pillars to get across the vat. Make sure to avoid the swinging hooks, but if you "go for a swim" you can use the tunnel under the water to make your way back and try again.
Kill two more guards and take their flares and the medkit. Now you should be at the top of a long slide which dumps you right into a vat of toxic waste. About halfway down the slope is a hole which contains Secret #1; the Stone Dragon. You can slide forward and into the hole where you can claim your statue before climbing out and continuing your slide towards the toxic waste. When you reach the bottom you can jump across the waste to the other side.
Climb up the ladder and grab some ammo then check out the slope beneath the hole. Jump in the hole and grab the ledge as you slide off backwards. There is a guard on duty below so get ready. Drop down and grab and pull up while drawing your guns to kill the guard. Take all that ammo he leaves behind. The door with the Blue Key Lock is near your present location and the Blue Key Card is in a hole on the other side of the room. Jump into the small opening from the catwalk. You will slide down the slope and into the hole where you can take the card then follow the tunnel back around and up the ladder and to the door with the Blue Key Lock.
Get ready for action as you enter this next room. Four Dobermans and a guy with a flamethrower are just waiting to take you on. Dispose of the dogs while keeping a safe distance from the guy with the fire. Take him out QUICK with the biggest gun you have. It's best to kill these guys before they ever get off a shot. If they do manage to "flame-on" then just backup and wait until it is safe to move in and finish them off.
There should be four doors; two of which have wheels you can spin to open them with. One door leads to stairs going up and the other has stairs going down. Go down these stairs and eliminate the workman then push the box out of the way to reveal a control panel with a missing Chip. Make a note of the circular saw as you will be coming back shortly.
Before you jump into the water make sure you have found the only place that you can get back out. Now dive in and tease the frogman so he follows you to the surface. Climb out and fill him with lead then dive back in and explore the tunnel he was guarding. You should find two switches inside the tunnel - flip them both and continue along this passage making a series of right turns. A door should open as your get near, so go through and turn left to arrive back at the large pool. Go up the stairs and take care of the two guards and the workman who are guarding a helicopter. Grab the medkit, ammo and shells when the shootout is over.
Cross the large room and enter the smaller room with some burners in the floor, a trapdoor, a switch and a button. Flip the switch on the right and head forward and drop through the trapdoor to collect the M-16 and some clips. Quickly climb out and return to the button before the burner turns back on. Flip the switch again then jump to the left and push the button then make a dash across the room, jumping OVER the trap door and grab the Chip. Quickly do a reverse roll and head back out of this room and to the control panel where you can use the Chip.
After you insert the Chip, the door open. Run down the ramp and shoot the workman across the pool from the safety of the hallway, then run across to the medkit he dropped. A flamethrower is to your left and he opens fire as you run past. Take care of him from the opposite side of the pool then go to the right of the orange tank to open a secret panel. Go inside and press the button, then return and dive into the pool to obtain Secret #2; the Jade Dragon from the now-opened grate at the bottom.
Exit the pool and grab the Harpoon Gun which is next to the scuba gear then dive back in and head down the underwater tunnel. When you hear the breathing of approaching frogmen, retreat back to dry land and kill both of them from the safety of the shore. Now jump back in and swim through the passage to emerge in another room. Exit on the low ledge on the right and take care of those two workmen. Now you can jump up to the top of the wall and flip the switch to open a door back in the previous room.
Return to the previous room where a frogman and two workers are waiting for you. Kill them all and take the medkit and Uzi clips as your reward. Go through the door you just opened and use the switch the crane will move allowing you to climb up and over to the other side of the pool.
Head for the corner and jump over the boxes and press the button to get a view of the room with the door you "unsealed" earlier. Head for that room now killing the two guards and their dogs. When you arrive, drop down and enter the tunnel and arrive at the central chamber. A guard tries to distract you from his friend with the Flamethrower who is sneaking around the corner so take out the flamethrower guy first then finish off his friend. Grab the second Chip which we need for that circular saw we passed by earlier. Return there now.
Insert the Chip and the blade disengages and you can now take the Red Key Card before returning to the central chamber. Use your new key card and drop down to take care of the Rig Boss. Continue into the room with the water and take care of the remaining Rig Workers. Take the medkit and also the harpoons which are over by the scuba tanks. Continue through the door until you enter a large room.
Kill the Rig Boss and the guard from above then enter the open door to the small room to obtain Secret #3; the Gold Dragon. If for some reason this door is shut, you will need to return to the room where you used the Red Key Card and flip the switch. The switch toggles this door open and closed, but the door should be already open assuming you didn't go flipping switches earlier without me telling you to. Once you have the statue you can approach the body in the middle of the room to take a submarine ride and exit this level...