Greece - Tomb of Tihocan (part 4)
Tomb Raider Anniversary - Visual Walkthrough
Alright, now get back up (using either the first method or the long stair) and flood the second level as well.
Swim now to the platform.
Then jump from the platform to the platform nearby.
You need to position the platform so you can reach the green with the 3 fountains.
And you've finally made it!
Doesn't look too bad, eh?
Anyway, jump right in and you'll eventually end up in a cavern.
Get to the surface for some air and then get back, swim to the underwater tunnel nearby and you should end up at the temple.
Don't get out of the water though; the door is still closed, so you need to open it first.
There's an underwater channel that leads to a room with a switch, pretty much the opposite to where you came, also there's a room with an artifact near it.
Flip the switch and you're ready to enter the temple.