pigboat vs submersible

pigboat and submersible both are nouns.

Word	Noun	Adjective	Verb	Adverb
pigboat	Yes	No	No	No
submersible	Yes	Yes	No	No

As nouns, submersible is a hypernym of pigboat; that is, submersible is a word with a broader meaning than pigboat:

Other hypernyms of pigboat include submersible warship.

pigboat (noun)	submersible (noun)
a submersible warship usually armed with torpedoes	a warship designed to operate under water
	an apparatus intended for use under water

pigboat (adjective)	submersible (adjective)
	capable of being immersed in water or functioning while submerged