sandbank vs shoal

sandbank and shoal both are nouns.

Word	Noun	Adjective	Verb	Adverb
sandbank	Yes	No	No	No
shoal	Yes	No	Yes	No

As nouns, shoal is a hyponym of sandbank; that is, shoal is a word with a more specific, narrower meaning than sandbank:

sandbank: a submerged bank of sand near a shore or in a river; can be exposed at low tide
shoal: a sandbank in a stretch of water that is visible at low tide

sandbank (noun)	shoal (noun)
a submerged bank of sand near a shore or in a river; can be exposed at low tide	a large group of fish
	a stretch of shallow water
	a sandbank in a stretch of water that is visible at low tide

sandbank (verb)	shoal (verb)
	become shallow
	make shallow