Swim Mode for Tomb Raider III Demo
Press and hold L1 then press and hold X + SQUARE. Now tap R2 and quickly release all three buttons. You should now be SWIMMING in midair.

Now proceed through the rest of the game in the SWIM MODE, by pressing SQUARE.To return to normal tap R1. Notice that the background sounds are the same as if Laura was actualy underwater.

NOTE: While in SWIM MODE you cannot pick up items, activate switches or use weapons. You can use flares by pressing SELECT. Laura will not lose (Health) while in SWIM MODE.