Seabirds wheel over the green ocean, concentrating their attention on a shoal of fish feeding in the surface waters. One by one the birds dive, splashing into the depths and surfacing again with their catches. Suddenly a great turmoil churns up the water, and in a cloud of spray, pointed heads on long thin necks burst from the surface and shoot skywards, snapping and snatching at the wheeling flock. When they subside once more into the sea the flock of birds has scattered in panic, and many of their number have disappeared.