Military diving is underwater diving done by members of armed forces for military purposes.
Any method of diving may be used. It is the military purpose that makes it military diving.
Military diving for offensive purposes is usually done using rebreathers as they do not make much bubbles which can be seen by the enemy. These divers may be called frogmen or combat divers.
Othe military divers do work to remove obstructions and explosive devices like mines. They are called clearance divers.
Military divers may also do inspections and repair work on the bottoms of ships, and underwater work in support of military engineering operations.