If any of your friends ask how it works, give them this to read....

If any of your friends ask how it works, give them this to read.  It will explain it all.

http://www.google.com/patents/US20120102938

I understood this bit.

"From the foregoing, it is evident that the buoyancy actuator according to the present embodiment provides a float which is relatively lightweight and which can be rendered effectively inoperative in adverse conditions for preservation."