Davy Jones's locker vs sea bottom

Davy Jones's locker and sea bottom both are nouns.

Word	Noun	Adjective	Verb	Adverb
Davy Jones's locker	Yes	No	No	No
sea bottom	Yes	No	No	No

As nouns, Davy Jones's locker and sea bottom are synonyms defined as:

Other synonyms of Davy Jones's locker include Davy Jones, ocean bottom, ocean floor, sea floor, seabed.

Davy Jones's locker (noun)	sea bottom (noun)
the bottom of a sea or ocean	the bottom of a sea or ocean