Two mating sea angels flutter through the deep waters of the Arctic Ocean off the coast of Novaya Zemlya, an archipelago near northern Russia, in recently captured footage.

In the video, which was filmed by marine biologist Alexander Semenov, a single clearly visible sea angel is joined by a second one. The pair of sea slugs then swims through the water side-by-side in a flowing mating ritual that resembles a dance.

When two sea angels find each other, they turn out their reproductive organs and attach themselves to their partner’s body with a sucker to stay together during the mating process. This attachment leaves scars on their bodies, and some adult sea angels have up to four scars, which can indicate