Killer whale Kasatka and her calf Nakai showed scientists what they "do not do" to survive the first weeks after the baby is born. Ally the Weddell seal revealed her unexpected hunting tactic under the ice in Antarctica. Popolo the dolphin has revealed how he is able to dive for periods of time that are much longer than the best trained human diver can achieve. Other dolphins like Dodger have brought to the surface the secret strategy they use to avoid dangerous encounters with prey. Henry the harbor seal has shown scientists why murky, dark waters are no problem for him when it is time to find a meal. Readers join the scientists and their animal partners in an amazing adventure that will reveal secrets of these amazing aquatic mammals.