ship biscuit vs sea biscuit

ship biscuit and sea biscuit both are nouns.

Word	Noun	Adjective	Verb	Adverb
ship biscuit	Yes	No	No	No
sea biscuit	Yes	No	No	No

As nouns, ship biscuit and sea biscuit are synonyms defined as:

ship biscuit and sea biscuit: very hard unsalted biscuit or bread; a former ship's staple

Other synonyms of ship biscuit include hardtack, pilot biscuit, pilot bread.

ship biscuit (noun)	sea biscuit (noun)
very hard unsalted biscuit or bread; a former ship's staple	very hard unsalted biscuit or bread; a former ship's staple