Webster's Revised Unabridged Dictionary · 1913

Shoal

Shoal , noun

[Anglo-Saxon scolu, sceolu, a company, multitude, crowd, akin to Old Saxon skola; probably originally, a division, and akin to Icelandic skilja to part, divide. See Skill, and compare School. of fishes.]

A great multitude assembled; a crowd; a throng; -- said especially of fish; as, a shoal of bass.
Great shoals of people. — Bacon
Beneath, a shoal of silver fishes glides. — Waller

Shoal , intransitive verb

To assemble in a multitude; to throng; as, the fishes shoaled about the place. — Chapman

Shoal , adjective

[Compare Shallow; or compare German scholle a clod, glebe, Old High German scollo, scolla, prob. akin to English shoal a multitude.]

Having little depth; shallow; as, shoal water.

Shoal , noun

1.
A place where the water of a sea, lake, river, pond, etc., is shallow; a shallow.
The depth of your pond should be six feet; and on the sides some shoals for the fish to lay their span. — Mortimer
Wolsey, that once trod the ways of glory, And sounded all the depths and shoals of honor. — Shakespeare
2.
A sandbank or bar which makes the water shoal.
The god himself with ready trident stands, And opes the deep, and spreads the moving sands, Then heaves them off the shoals. — Dryden

Shoal , intransitive verb

To become shallow; as, the color of the water shows where it shoals.

Shoal , transitive verb

To cause to become more shallow; to come to a more shallow part of; as, a ship shoals her water by advancing into that which is less deep. — Marryat