Electric Rays are fairly common on the sandy areas between seagrass beds in shallow water just offshore. As are the Eagle Rays inside the reef where they come to feed, but they're usually closer to the reef which is harder to get to as it's not within swimmable distance for most mortals, or recommended to those that can with the amount of boat traffic.

There's tons of good stuff to see in the grass beds around docks so long as you're careful to keep an ear out for boats coming and going and you need to be patient, have a good eye, go often and be prepared to see a lot of seagrass! As the nursery grounds for many juvenile fish who rely on camouflage to survive it takes a bit of time to find things but there are lots of species and I have see on a reasonable occurrence Batfish, SeaHorses, Octopus, Lobster, King Crabs, Sailfin Blennies, Various Shrimp and Shellfish, and lucky enough to see once each a Bull and a Lemon Shark.