Please be aware that there are no "rules" for the tubing adventure. You're more or less taken to a place or tourists to pay some cash, grab a tube and head down the current. I'm a bigger guy and had a blast. Unfortunately, I had a blowout when I tried to lean in to bounce off the wall and found a sharp tree branch underwater. The sound of the tube blowing out under the water had to be one of the funniest things ever. However, it wasn't so funny when I realized how strong the current was. Fortunately, I was near the end and one of the "guides" lent me one of his tubes while he swam down the rest of the way.
It was a great time!