Plunges into water (5)
I believe the answer is:
dives
'plunges into water' is the definition.
('dive' can be a synonym of 'plunge into water')
This is the entire clue.
(Other definitions for dives that I've seen before include "Rich man's" , "Pools entries" , "Plunges head first" , "sort of nightclubs?" , "Man, loaded" .)