Plunging oneself into water (6)
I believe the answer is:
diving
'plunging oneself into water' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for diving that I've seen before include "Going underwater" , "Plunging into water - falling in the air" , "Principles of right and wrong" , "Throwing oneself into water" , "Plunging oneself into water" .)