Swim's alternative (4)
I believe the answer is:
sink
'swim's alternative' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sink that I've seen before include "Drop beneath the water - kitchen appliance" , "Slump" , "Excavate (a well)" , "Scene of iniquity or washing up" , "Washing facility" .)