Normal
On the tours that I have been on, they provided snorkel vests and they required you to wear them. They are less bulky than a life jacket but give you enough bourancy that you just float. You blow them up with the amount of air that you want, then you can release the air if you want to dive down. The angle of the head allows you to still look down, where as a life jacket is designed to keep your face out of the water. Also, the salt water makes you float some. I think a non-swimmer could do it, if they were not just terrified of jumping into the water as a non-swimmer. You might consider a walk-in type tour as opposed to a boat tour as those usually everyone just jumps overboard.
