3 adjectives to describe porpoise

And the thirty-first of May, helter-skelter through the blue, Like a crowd of frightened porpoises a shoal of sharks pursue, Came crowding ship on ship to Saint Malo on the Rance, With the English fleet in view.

Tom and Annie Lee, however, stood quietly by the bulwarks, holding fast on, as they had promised their mother that they would, and though longing to join in the fun, they tried to amuse themselves with watching the foaming waves the swift vessel left behind, and the awkward porpoises which seemed to be rolling themselves with delight in the sunny waters.

The sport was infectious, and soon fat old Castleman was puffing like a tired porpoise, and sedate old Karl de Pitti was in the chase.

3 adjectives to describe  porpoise