Coral reef's place (3)
(Other definitions for sea that I've seen before include "North, say" , "E.g Aral or Weddell" , "The Aegean, for example" , "Lesser ocean" , "The briny" .)
(Other definitions for ocean that I've seen before include "tons of water" , "Main" , "An immense expanse of sea" , "Great sea" , "eg Indian, Pacific" .)