Does the human body have to decompress after surfacing in a submarine?

No - Submarine crews live and work within the inner pressure hull, which is pressurized. The outer hull/superstructure of most submarines are mad of flexible steel, which contracts and expands with the changing depths as the bot travels.

Decompression is only necessary for divers who have been exposed to sea pressure, which compresses the nitrogen in the bloodstream . Coming to shallower depths without decompressing properly (it depends on the depth and time at depth, as well as the gas being used for diving) can lead to the compressed nitrogen in the blood to be released too quickly, resulting in the Bends, a painful, crippling, and often deadly result of improper decompression.

The most common example of a gas being released in a liquid after being compressed into it are sodas - when you open the top of the can or bottle, the compressed CO2 is rapidly released as a gas back into the liquid.