bathyal district vs sea bottom

bathyal district and sea bottom both are nouns.

Word	Noun	Adjective	Verb	Adverb
bathyal district	Yes	No	No	No
sea bottom	Yes	No	No	No

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

bathyal district: the steep descent of the seabed from the continental shelf to the abyssal zone
sea bottom: the bottom of a sea or ocean

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

bathyal district (noun)	sea bottom (noun)
the steep descent of the seabed from the continental shelf to the abyssal zone	the bottom of a sea or ocean