www.pbs.org/wgbh/nova/lasalle/buoyquestion.html

This virtual simulator allows students to experiment with the buoyancy of a submarine.

science.howstuffworks.com/transport/engines-equipment/hydrau

This site teaches you how Hydraulic machines work through written text.

www.onr.navy.mil/focus/blowballast/sub/work2.htm

This site show you how Archimedes' Principle causes Submarines to be able to move from below the water to floating on top.