Coral ___ (4)
(Other definitions for sea that I've seen before include "All at . . . - totally confused" , "Part of ocean" , "The deep" , "Lesser ocean" , "The Aegean, for example" .)
(Other definitions for reef that I've seen before include "Ridge of coral near the sea surface" , "Ridge of rock just below ocean surface" , "Shoal; take in (sail)" , "endangered habitat" , "Submerged ridge of rock or coral near the surface" .)