Watch YouTube user Xraise Cornell create a homemade horizontal vortex ring generator. When a small burst of air is released into a toroidal or poloidal vortex — essentially a spinning donut of water — it shapes the air into its own ring along the water’s trajectory, creating a vortex ring or a bubble ring.
While we have not made this invention (yet), it looks like a lot of fun. Or of course, with a lot of practice, you could try to make them with no materials at all, just like the dolphins do. Just remember to always be safe. Adult supervision is recommended when using tools or trying experiments underwater.