In the clip, you see two separate rings moving through deep water.
The pair collide and then latch on to each other, appearing to be co-existing.
But then they separate again as one rises towards the top of the water and the other sinks to the seabed.
The footage then cuts out before we know what happens next.
The clip, believed to be filmed in Australia, was uploaded to Reddit earlier today with the title: “Air rings collide underwater.”
And since then it has received more than 42,000 up votes.
But viewers cannot agree on what is going on.
One comment read: “I have not got a clue what I’m looking at, but I’m mesmerised.”
And another added: ”I don’t know why but this makes me think of aliens.”
But some believed they had cracked the mystery, revealing it could be a vortex ring.
Also known as bubble rings, these occur when air bubbles occupy the core of the circle.
Nearby water then spins as it travels through the water.
The physics behind this phenomenon is still being studied in fluid dynamics.