Crossword Genius

One long in the water? Leave rock (6,3)


I believe the answer is:

conger eel

I'm a little stuck... Click here to teach me more about this clue!

'one long in the water?' is the definition.
I can't judge whether this defines the answer.

'leave rock' is the wordplay.
'leave' becomes 'conge' (I've seen this in other clues).
'rock' becomes 'reel' (reel can mean to rock around).

Can you help me to learn more?

(Other definitions for conger eel that I've seen before include "Predatory sea creature" , "Large slippery fish" , "swimmer" , "Predatory fish" , "long haul?" .)

I've seen this clue in The Independent.
Want a hint initially instead of a full solution? Install my app