TIL that sea otters have a pocket set across their chest in which they carry their favorite rock. This rock is used to crack open shellfish and each rock is unique to that specific otter. They tend to hold onto the same rock for life.

This aquatic member of the weasel family is found along the coasts of the Pacific Ocean in North America and Asia. The sea otter spends most of its time in the water but, in some locations, comes ashore to sleep or rest. Sea otters have webbed feet, water-repellent fur to keep them dry and warm, and nostrils and ears that close in the water.

Sea otters often float at the water's surface, lying on their backs in a posture of serene repose. They sleep this way, often gathered in groups. Otters sometimes float in forests of kelp, or giant seaweed, in which they entangle themselves to provide anchorage in the swirling sea.

These aquatic otters do more than sleep while floating on their backs. They are often seen with a clam or mussel and a rock that has been deftly snared from the ocean floor. Otters will place the rock on their chests, and repeatedly smash the shellfish against it until it breaks open to reveal the tasty meal inside. They also dine on such aquatic creatures as sea urchins, crabs, squid, octopuses, and fish.

Sea otters are the only otters to give birth in the water. Mothers nurture their young while floating on their backs. They hold infants on their chests to nurse them, and quickly teach them to swim and hunt.

Sea otters are meticulously clean. After eating, they wash themselves in the ocean, cleaning their coat with their teeth and paws. They have good reason to take care of their coats—it helps them to remain waterproof and insulated against the cold. Sea otters have thick underfur that traps air to form an insulating layer against the chilly waters (they have no insulating fat). This coat is invaluable to otters, but it has worth to some humans as well.