If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
look for lost artefacts under the water. There are bubbles that appear and disappear. You can only move inside these bubbles. If the bubble you are currently in disappears, you fall down. If you fall to the bottom, you're dead. Collect the required number of artifacts to pass to the next level. There also are bonuses and traps that affect your game play.
A, S, D, F - Move.
Mouse - Teleport (If fully charged).