Dolphins blow vortex rings, apparently because they enjoy doing it.

[Spinnor]

https://d2r55xnwy6nx47.cloudfront.net/uploads/2020/09/0903_TurbulenceBlobs_Dolphins-1920x1080.mp4

From, https://www.quantamagazine.org/an-unexpected-twist-lights-up-the-secrets-of-turbulence-20200903/

 

[kuruman]

They already tried smoke rings but it didn't work very well.

 

[berkeman]

From, https://www.quantamagazine.org/an-unexpected-twist-lights-up-the-secrets-of-turbulence-20200903/

Dolphins are fun. One of my most memorable free diving experiences was in Hawaii on the northwest shore of Maui with some Spinner Dolphins. They had followed a big tourist catamaran into a bay, entertaining the folks on the cat with their jumping and spinning behavior, and I kicked out toward them to see if I could get a closer look.

When the cat turned and headed out of the bay, the Spinners stayed and I got into the middle of them to see if they were friendly. Unfortunately I was a bit out of breath from kicking hard to get out to them, but I was still able to stay with them a ways down on surface dives, with them letting me be fairly close. It was so cool to be surface diving with them, spinning slowly down alongside them. Very cool and special memory.

https://en.wikipedia.org/wiki/Spinner_dolphin

BTW, funny coincidence that this thread was started by @Spinnor