While diving animals are capable of both long-duration and deep dives, their normal behavior does not routinely approach these limits of time and depth. Studies of the physiologic and biochemical capabilities of diving species have defined the maximum limits of their underwater periods. However, by also studying their diving behavior, we can examine how diving animals most efficiently work within those limits. If we assume for example that the behavioral goal of a foraging seal is to spend as much time underwater as possible, then it must also minimize time at the surface and make many repetitive dives instead of single, longer dives that require long surface recovery periods. To understand the efficiency of bout diving, we must study the physiologic impact of many repetitive dives and how the seal manipulates its behavior to both stay within its physiologic limits and to maximize time underwater.