Richkeller, scubabudie is right on the mark in his post. Ft Getty is open to the public. There is a fee to enter. There is easy access to launch a kayak and it's a short 1/2 mile paddle to Dutch Island. The east side northern end of the island has a drop off to about 50fsw with a rocky wall that ends on a sandy bottom. The current running thru there can be very strong and slack is the best time to dive. The southern end still east side is more sloping to the bottom. There is also a barge wreck off the southern tip of the island about 1/2 mile to the south it is marked by buoys and is a good dive if you hit the vis right. If you like a challenge Beavertail point is a beautiful dive site that has deeper water stronger currents and more ocean swells on the East side than the West side which is the West Passage. There are usually some very big Tog and stripers that inhabit the East side. The bottom is about 80fsw but if you look you'll find deeper spots, you can hit your limit there whatever is it up to 200fsw. The East Passage is I think the deepest natural channel to a bay on the east coast but I could be mistake. It is deep however. The wreck Cape Fear in the East Passage is almost 170fsw and it is almost a shore dive! There are many interesting dives here in RI and a lot of them are easy. Newport, Gooseberry Island is a great dive. There are 2 natural underwater arches on the south west end of the island that are beautiful photo shots when the vis is good, and the vis can be very good there. I had almost 30' vis there last June! It also attracts many varied species of fish and of course BUGS. On the east side of the island there is a huge rock on the bottom in about 30fsw that the inside was ground away and looks like a giant bowl. Gooseberry is accessible from Green Bridge Cove and is about 1/2 mile paddle. Also from Green Bridge Cove is Prices Neck a former AAA gun range area for the US Navy. There are still 40MM AAA shells to be found there, I found one last year.
Kings Beach is also an easy launch point, from there Seal Rock about 600 yards to the south west, it can be seen from the beach. Price Neck can also be accessed from Kings Beach. If you need more info PM me these have been my stomping grounds for 4 decades. Dive RI!