Plunged in canal, reportedly (6)
I believe the answer is:
ducked
'plunged' is the definition.
(ducking is a kind of plunging)
'canal reportedly' is the wordplay.
'canal' becomes 'duct' ('duct' can be a synonym of 'canal').
'reportedly' indicates a 'sounds like' (homophone) clue.
'duct' is a homophone of 'DUCKED'.
'in' is the link.
(Other definitions for ducked that I've seen before include "Bobbed down" , "Bowed head to avoid missile" , "Avoided as mallard might" , "Went down" , "Dipped" .)