What happens to human lungs when they are succumbed to the same type
of pressure fish encounter when they go to the sea floor?

The lungs will experience a lower pressure inside them compared to the
high pressure at the bottom of the ocean. This will cause the air to
be pushed out of them. If you press on the outside of a plastic bottle
(just like the high ocean pressure) then the air in the bottle
('lung') will be forced out.

they go KAPUT! 

To understand The Physics of Underwater Diving: Pressure Lesson

go to 
http://www.earthscape.org/r1/noa11/noa11f2.html