Some folks just can't get comfortable with scuba gear. This scooter may be just the thing for them.
You sit on it, put your head in, they lower you in the water...and away you go! No scuba training required. You get about 50 minutes of air. Of course, you can't go to all the places that a regular diver can go, but you don't have to learn to suppress that panic feeling either :-)
There are plenty of resorts that have these for rent... and if you are in Tenerife, just look for Safari BOB Diving .