Snorkelling spots for lough party reviewed (5)
I believe the answer is:
reefs
If this is the answer, I'm afraid I cannot explain it.
Can you help me to learn more?
(Other definitions for reefs that I've seen before include "Groups of submerged rock" , "coral banks" , "Ridges of rock or sand beneath sea surface" , "Submerged ridges of rock or coral near the surface of water" .)