Snorkeling areas (5)
I believe the answer is:
reefs
'snorkeling areas' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for reefs that I've seen before include "coral banks" , "Groups of submerged rock" , "Submerged ridges of rock or coral near the surface of water" , "Ridges of rock or sand beneath sea surface" .)