continental shelf vs sea bottom

continental shelf and sea bottom both are nouns.

Word	Noun	Adjective	Verb	Adverb
continental shelf	Yes	No	No	No
sea bottom	Yes	No	No	No

As nouns, sea bottom is a hypernym of continental shelf; that is, sea bottom is a word with a broader meaning than continental shelf:

continental shelf: the relatively shallow (up to 200 meters) seabed surrounding a continent
sea bottom: the bottom of a sea or ocean

Other hypernyms of continental shelf include Davy Jones's locker, Davy Jones, ocean bottom, ocean floor, sea floor, seabed.

continental shelf (noun)	sea bottom (noun)
the relatively shallow (up to 200 meters) seabed surrounding a continent	the bottom of a sea or ocean