Animal that sleeps while floating on its back

SEAOTTER

["This marine mammal often holds hands while resting to avoid drifting apart."]

This clue describes a sea otter, which is known for floating on its back while sleeping. The answer "SEAOTTER" combines "sea" and "otter" to directly name the animal. There’s no wordplay here—it’s a straightforward definition pointing to a unique behavior of this marine creature.