Animals adjust their foraging behavior to environmental conditions such as lights, turbidity and prey density. However, there have been few studies on the adjustments of foraging dive to the underwater conditions. In this study, we clarified the relationship between foraging dives and the type of prey. Feeding experiments were made on a diving bird, the little grebes Tachybaptus ruficolis, in the aquarium. Four kinds of prey, each of which escaped in variant speed and motion, were fed to an individual grebe. 2D motional analysis was conducted by using lateral views to quantify the body movements in foraging dives. It was found that little grebes have two styles of dive; with or without head bobbing. A rapid-swimming prey triggered non-bobbing dives of the grebe, and two kinds of slow-swimming prey triggered head-bobbing dives. Head-bobbing consisted of head extrusion and fixation, and the head fixation time became longer in proportion to the degree of changing in direction. The results show that the diving style relies on necessary swimming speed to catch prey, and that the complexity of prey’s motion affects the foraging dives. Since head fixation in birds is known as the function of visual perception, it is likely that the diving bird adjusts the perceptive duration to the degree of cognitive difficulty.