shoal

nouns

a sandbank in a stretch of water that is visible at low tide
shoal
is derived from
shoaly
is a type of (narrower)
a submerged bank of sand near a shore or in a river; can be exposed at low tide
sandbank
a stretch of shallow water
shallow, shoal
a large group of fish
"a school of small glittering fish swam by"
school, shoal

verbs

make shallow
"The silt shallowed the canal"
shallow, shoal
become shallow
"the lake shallowed over time"
shallow, shoal