This is a popular site in Rhode Island. Ft. Wetherill, Jamestown. 3 possible entries, from the parking lot, facing the water. To your right is a boat ramp, this is where the open water classes take place. It is also a deep dive if you travel along the left wall of the cove to the end where it drops to about 100'(33m)
You can also enter the left cove, a short walk down a narrow path and a steep hill. Here you will follow along the right wall of the cove and end up in the same area if you go to the end of the wall.
You can also enter through the DEP station(Bull Point) this is a pretty tricky climb down a rock hill. once in the water it is a shorter swim to hit deeper depths. Avoid this entry with any kind of wind out of the south west.