Sea otters hold hands while sleeping so they don't drift apart.

Sea otters spend most of their lives in the water and often rest floating on their backs in groups called rafts. To keep from drifting away from each other on the current or waves while asleep, they’ll hold paws with one another, and mothers often wrap themselves and their pups in strands of kelp for extra security.

This social clustering also offers safety in numbers against predators. Rafts can range from just a couple of otters to, historically, groups of a thousand or more, though most rafts today are much smaller as a result of past population declines from hunting.