submersible has 2 distinct synonyms spread across 2 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its 2 recorded opposites are surface ship, nonsubmersible.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
an apparatus intended for use under water
a warship designed to operate under water
capable of being immersed in water or functioning while submerged
“a submersible pump”
Synonyms, antonyms and the broader and narrower relations for submersible come from Princeton University’s WordNet. Full sources and licences.