sea god vs deity

sea god and deity both are nouns.

Word	Noun	Adjective	Verb	Adverb
sea god	Yes	No	No	No
deity	Yes	No	No	No

As nouns, deity is a hypernym of sea god; that is, deity is a word with a broader meaning than sea god:

sea god: a deity that personifies the sea and is usually believed to live in or to control the sea
deity: any supernatural being worshipped as controlling some part of the world or some aspect of life or who is the personification of a force

Other hypernyms of sea god include divinity, god, immortal.

sea god (noun)	deity (noun)
a deity that personifies the sea and is usually believed to live in or to control the sea	any supernatural being worshipped as controlling some part of the world or some aspect of life or who is the personification of a force