Waterborne gambler? (6)
I believe the answer is:
punter
'gambler?' is the definition.
(punter is a kind of gambler)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for punter that I've seen before include "One betting; 4's prey (slang)" , "boater" , "Informally, a customer or someone who bets" , "Person who bets" , "Gambler; customer" .)