The Collaborative International Dictionary of English v.0.48:

Shoaling \Shoal"ing\, a.
   Becoming shallow gradually. "A shoaling estuary." --Lyell.
   [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]