Various people going under (6)
I believe the answer is:
divers
I believe this clue is a double definition.
'various' is the first definition.
(I've seen this before)
'people going under' is the second definition.
(divers go under the sea)
(Other definitions for divers that I've seen before include "Underwater, they are many and various" , "Plungers" , "Several; frogmen" , "Various; frogmen" , "Several underwater workers" .)