ACCORDING to the 20-10 seconds rule the average period of the dive in 6 feet of water is 20 seconds, and it is suggested that of this period, 10 seconds are spent in going up and down and 10 seconds on the bottom in search of food (Dewar, 1924). As a direct approach to the problem of the distribution of the time spent under water is almost impossible owing to the wildness of the birds and the normal turbidity of the water, other means had to be found to test the validity of the suggestion. When the bird dives at a fairly steep angle by the propulsant action of the feet alone, a column of water is forced up to the surface by the action of the feet, and the place of immersion is marked by a limited area of up-welling water mixed with bubbles of air. The up-welling I call " turmoil." Turmoil begins when the bird is immersed and continues for some time after the bird reaches the bottom. Turmoil ends abruptly and its duration can be timed with a stop-watch. A perfectly calm day is essential for correct timing. When the bird reaches the bottom the up-welling of water ceases to be produced, since the direction of the foot-stroke becomes more oblique and much less thrust is required to hold the bird on the bottom. Turmoil does not end at the moment the bird reaches the bottom, because the water, which is forced upwards, takes time