For those who like their dives easy, they hardly come much easier than Bonnie's Arch. It's close enough to reach from shore, but for pure dive laziness, your best bet is to descend to it from a boat.
You could spend almost the entire dive just around the arch, which is the real secret to this spot. Most divers descend, swim through the arch, then move on to the nearby reefs. Instead, take your time there. There are some nice tube and barrel sponges at the base of the arch worth poking around. There are usually a few cleaner shrimp and decorator and arrow crabs hiding out and some juvenile spotted drum, if you're lucky; if you hang around long enough, the French and gray angels will pop over from the reefs to see why the heck you aren't paying attention to them. But you'll have to work a little harder to find the crocodile statue that was placed at the base of the arch. Most divers just swim right past it, and with each passing year's growth, it's definitely getting harder to find, even when you know it's there.
Filefish seem to like the shade beneath the arch, and there are usually a few tarpon traipsing about, especially in the afternoons.
The best dives don't have to be difficult. Bonnie's Arch is worth the ease.