high water vs high tide

high water and high tide both are nouns.

Word	Noun	Adjective	Verb	Adverb
high water	Yes	No	No	No
high tide	Yes	No	No	No

As nouns, high water and high tide are synonyms defined as:

Other synonyms of high water include highwater.

high water (noun)	high tide (noun)
the tide when the water is highest	the tide when the water is highest