Dotted about the swelling surface there would be the heads of plenty of swimmers--men and lads--some going smoothly along, mounting the rollers as they came in, and descending softly into the hollows; others again swimming to meet each wave, then rising a little, and with a plunge like a duck or one of the great bronze-black shags, or cormorants, that sat upon the rock-shelves, diving right through the mass of water, to come out fairly on the other side.