The Collaborative International Dictionary of English v.0.48:

Shoal \Shoal\, a. [Cf. Shallow; or cf. G. scholle a clod,
   glebe, OHG. scollo, scolla, prob. akin to E. shoal a
   multitude.]
   Having little depth; shallow; as, shoal water.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shoal \Shoal\, n.
   1. A place where the water of a sea, lake, river, pond, etc.,
      is shallow; a shallow.
      [1913 Webster]

            The depth of your pond should be six feet; and on
            the sides some shoals for the fish to lay their
            span.                                 --Mortimer.
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            Wolsey, that once trod the ways of glory,
            And sounded all the depths and shoals of honor.
                                                  --Shak.
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   2. A sandbank or bar which makes the water shoal.
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            The god himself with ready trident stands,
            And opes the deep, and spreads the moving sands,
            Then heaves them off the shoals.      --Dryden.
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The Collaborative International Dictionary of English v.0.48:

Shoal \Shoal\, v. i.
   To become shallow; as, the color of the water shows where it
   shoals.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shoal \Shoal\, n. [AS. scolu, sceolu, a company, multitude,
   crowd, akin to OS. skola; probably originally, a division,
   and akin to Icel. skilja to part, divide. See Skill, and
   cf. 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.
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         Beneath, a shoal of silver fishes glides. --Waller.
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The Collaborative International Dictionary of English v.0.48:

Shoal \Shoal\, v. t.
   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.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Shoal \Shoal\, v. i. [imp. & p. p. Shoaled; p. pr. & vb. n.
   Shoaling.]
   To assemble in a multitude; to throng; as, the fishes shoaled
   about the place. --Chapman.
   [1913 Webster]

WordNet (r) 3.0 (2006):

shoal
    n 1: a sandbank in a stretch of water that is visible at low
         tide
    2: a stretch of shallow water [syn: shoal, shallow]
    3: a large group of fish; "a school of small glittering fish
       swam by" [syn: school, shoal]
    v 1: make shallow; "The silt shallowed the canal" [syn:
         shallow, shoal]
    2: become shallow; "the lake shallowed over time" [syn:
       shallow, shoal]

Moby Thesaurus II by Grady Ward, 1.0:

98 Moby Thesaurus words for "shoal":
   a mass of, a world of, ankle-deep, army, bank, bar, barrier, bevy,
   bunch, cloud, clutter, colony, coral heads, coral reef, covey,
   cursory, depthless, drift, drive, drove, epidermal, flat, flight,
   flock, flocks, ford, gam, gang, hail, herd, hive, hook, host,
   ironbound coast, jam, jejune, kennel, knee-deep, large amount,
   ledges, lee shore, legion, light, litter, lots, many, masses of,
   mob, muchness, multitude, nest, not deep, numbers, on the surface,
   pack, pitfall, plurality, pod, pride, quantities, quicksands,
   quite a few, reef, rockbound coast, rocks, rout, ruck, sandbank,
   sandbar, sands, school, scores, shallow, shallow-rooted, shallows,
   shelf, shoal water, shoals, skin-deep, skulk, slight, sloth, spit,
   superficial, surface, swarm, thin, throng, tidal flats, tidy sum,
   trip, trivial, troop, undercurrent, undertow, unprofound, wetlands,
   worlds of