frog ‧ man /ˈfrɒɡmən $ ˈfrɑːɡ-, ˈfrɒːɡ-/ BrE AmE noun ( plural frogmen /-mən/) [countable] British English
someone who swims under water using special equipment to help them breathe, especially as a job SYN diver :
Police frogmen have been searching the lake looking for a weapon.