Instructions
Press the "W" key to swim forward, the "S" key to swim back, and the "A" and "D" keys to swim sideways. The controls for swimming are identical to the controls for walking.
Hold down the left mouse button and use your laptop's trackpad to change the direction of your character while swimming. For example, holding "W" and using the trackpad to have your character look to the left causes him to swim toward the left.
Press the "X" key to have your character dive at any time.
Press the space bar to have your character surface any time he is under water.