We did 7-mile on our own, last December. It was great. They have a bar too, but we warned, the drinks are BIG, and like 10 bucks in u.s. You can rent snorkel gear fairly cheap at the beach, and there is a 'nice' reef to look at...
our friends were SOOO mad cuz someone was being completely rude and was walking on it (it dies from touch)
Also, don't miss this, it wasn't much more cost, go to 'Hell' they have a sovernir shop, and you can mail some postcards, and they have some stuff to look at....
it was interesting to say I've been to 'Hell' and back...LOL...
We did Carnival so we went to Belize too, and did the Cave Tubing, and there again the orginal 'natives' named one of the tubes 'Hell' so we went to 'Hell' twice... LOL...
but 7-miles is pretty.