It is called Snuba, a hybrid of scuba and snorkeling where you can experience breathing underwater without taking the scuba training. On the surface is a raft where your 20-foot-air-line is attached while you can experience the watery depths. Although only offered on minimal beaches in Florida, California and Hawaii, the 
sport began in the 1980s when a California diver group developed Snuba International. The Caribbean caught on and now tourist from Aruba to Truks and Caicos have caught the Snuba bug.
Snuba starts with safety procedures and a training session. Then you put on your flippers, weight belt, mask and a breathing regulator attached to a long tube. After a few minutes of practice in the shallows, you are out in deeper water and enjoying the new found ability of underwater breathing. Everyone diving with you are all in the same area so air lines can get tangled if you are not careful and a tug on your mouthpiece will warn you of that. But the thought of any malfunction is non-existent since you are not deep by any means and it is a short trip to the surface.
This experience can only leave you wanting more and consider the thought of taking actual scuba diving classes.