Sea otters hold hands when they sleep so they don't drift away from each other.

Sea otters hold hands when they sleep so they don’t drift away from each other.

Sea otters sometimes hold each other’s hands (or paws) to prevent them from floating out to sea or drifting too far from their group while sleeping. Huge ocean waves or strong water currents can unpredictably carry a sleeping sea otter away, so sea otters must stick physically close to each other to maintain the rafts’ integrity and stay safe.

Source