Deep-sea
Deep-sea , adjective
Of or pertaining to the deeper parts of the sea; as, a deep-sea line (i. e., a line to take soundings at a great depth); deep-sea lead; deep-sea soundings, explorations, etc.
2.
at some distance from the shore; as, deep-sea fishing.
3.
taking place in the deeper parts of the sea; as, deep-sea exploration.