Bight or bay (5)
I believe the answer is:
inlet
I believe this is a double definition.
'bight' is the first definition.
(thesaurus)
'bay' is the second definition.
(I've seen this before)
(Other definitions for inlet that I've seen before include "Coastal bay" , "Arm off a larger body of water between headlands" , "Small arm of the sea" , "Fjord" , "Bay or recess" .)