How Does Pressure Affect the Buoyancy of a Hollow Spherical Bobber?

[jabbie3]

Homework Statement

http://wug.physics.uiuc.edu/cgi/courses/shell/per/phys101/ie.pl?11/bobber#waypoint)"

Homework Equations

F=P_bottomA-P_topA

The Attempt at a Solution

I'm not really sure where to start..I am still trying to understand fluids.
It just doesn't feed well in my head and so I am trying to get help.
Thanks for any help!

 

[Delphi51]

The upward buoyant force on a submerged object is equal to the mg for the mass of water it displaces.