Maneuver the sub back and forth, avoiding the rocks and mines. Descend Perry to the lake bed to grab the sponges from the crabs then drop them into the Suction Vortex to clog it up. There are three levels. Watch out for the Jellyfish, and try not to annoy Candace too much with those gas bubbles.

Left / Right Arrow Keys - Move Phineas.
Spacebar - Turn Around.
Up Arrow Key - Extra speed boost.
Down Arrow Key - Grab / Drop.