To get to Hellshire, take a city bus to Halfway tree, then a minibus to (I forget), and then a cab the rest of the way. This is the local beach where I was warned not to go because it's where the "riff-raff" go. But this ended up being one of my favorite places in Jamaica! You can lay out on a big wooden bench in the shade, sunbathe on the sand, or go in the water. Don't expect waves to ride, though, as the water is pretty calm. Although the shop keepers will do their best to watch your bags if you leave them on the bench, it's best for someone to stay behind with valuables while others are in the water. (A friend's phone was stolen there).
Be sure to get some fish (although you will get ripped off as a tourist). Get a bamboo cup from Bamboo Bobby. They're really neat and really cheap, and he'll carve it right there. People will also approach you trying to sell CDs, bracelets, flip-flops, and ganja. Also, bring your dominoes, because there are plenty of tables in the restaurants to play. (And when I say restaurant, I mean stick hut).