Davy Jones's locker vs seabed

Davy Jones's locker and seabed both are nouns.

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

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

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

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