Boat causes waters to rise (5)
I believe the answer is:
sloop
'boat' is the definition.
(sloop is a kind of sailing vessel)
'waters to rise' is the wordplay.
'waters' becomes 'pools' (pool is a kind of water).
'to rise' is a reversal indicator.
'pools' backwards is 'SLOOP'.
'causes' is the link.
(Other definitions for sloop that I've seen before include "One-masted sailing ship" , "Type of sailing boat" , "one going to sea" , "Single-masted sailing boat" , "One-masted sailing boat" .)