frogman

/ˈfrɑɡˌmæn/
noun
  1. A person who swims underwater using special equipment such as a wetsuit, fins, and breathing apparatus, often for military or scientific purposes.
    • A frogman emerged from the water carrying a sample of coral.
    • The documentary followed a frogman as he explored a sunken wreck.
    • The navy frogman dove into the harbor to inspect the ship's hull.