(For those unable to access YouTube the clips show dolphins playing with what appear to be “smoke rings” except made of vortices under water - looks great but surely its fake?)
Yeah - it’s actually surprisingly easy for dolphins to manipulate air bubbles underwater, they can produce the air bubbles themselves, and have plenty of fins, muscle power, and speed for manipulation.
From what I understand (secondhand) it works by blowing an air bubble into the vortices created by their fins, and that’s why it’s so easy for them to get a ring shape.
… oh, yeah, and a lot of time on their hands…