high tide vs high water

high tide and high water both are nouns.

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

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

Other synonyms of high tide include highwater.

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