heavy swell vs ground swell

heavy swell and ground swell both are nouns.

Word	Noun	Adjective	Verb	Adverb
heavy swell	Yes	No	No	No
ground swell	Yes	No	No	No

As nouns, heavy swell and ground swell are synonyms defined as:

heavy swell (noun)	ground swell (noun)
a broad and deep undulation of the ocean	a broad and deep undulation of the ocean
	an obvious change of public opinion or political sentiment that occurs without leadership or overt expression