Practice, Practice, Practice
Have you ever been somewhere before on vacation and tried something new only to fall flat on your face trying. That happens to quite a few people when they go skiing for the first time. Their vacation can end up being more about falls and bumps than relaxing.
The same goes with some island activities. Scuba diving may look easy but it is not. You could try to take some local diving lessons before actually doing it in the open waters. These can be done before you go on vacation usually and may save you a ton of headaches and maybe some embarrassment when you go.
So be careful, and practice.