sea boat vs whaleboat

sea boat and whaleboat both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea boat	Yes	No	No	No
whaleboat	Yes	No	No	No

As nouns, whaleboat is a hyponym of sea boat; that is, whaleboat is a word with a more specific, narrower meaning than sea boat:

sea boat: a boat that is seaworthy; that is adapted to the open seas
whaleboat: a long narrow boat designed for quick turning and use in rough seas

Other hyponyms of sea boat include lifeboat.

sea boat (noun)	whaleboat (noun)
a boat that is seaworthy; that is adapted to the open seas	a long narrow boat designed for quick turning and use in rough seas