If you plan on going to Ocho Rios to score some weed...Don't! We heard many stories of tourists coming to the town to get pot and ironically they were approached with offers. If someone comes to you offering you weed, pass it up. These guys will bust you in a heartbeat. They wait around a corner with a car and lock you up. Not sure how that whole thing works because I had thought weed was legal there...I guess not. Anyhow, better safe than sorry. If that is the route you are hoping to take I suggest getting a guided tour on horseback at the beach...some of our group chose to do that instead and they managed to "make new friends." I personally don't care, but I figured I would try to help those out that do.
When you go swimming take care where put your feet. Some pieces of an ancient coral reef emerge among the sand and they are very sharp. So you could hurt your feet. In some places they are so many that it's better if you wear a pair of rubber shoes.
Remember you are in place where many people are poor. In Jamaica there are many hustlers, so you'll can often be bothered. Take the usual precautions, so don't wear gold jewels (to a friend of mine they snatched her little chain), take care of your wallet and your camera, don't loose sight of your backpack when you are on a free beach. Be kind but firm with them and try to understand if they can be dangerous. I am fatalist and think that if something must happen, it can happen everywhere.