If you are looking for something along the lines of Cat Rocks, the closest equivalent in RI would be Beavertail Point State Park at the south end of Jamestown. It is a fairly tricky entry/exit on the rocks like Cathedral and has some nice rock structures, canyons and swim throughs. Also like Cat Rocks, it is calm weather dive and you've really got to watch the slippery spots on the rocks.
If you dive Beavertail there are 4 different parking lots as you go around the point. The first one doesn't really have good shore access. It is theoretically possible (Shine's shore diving book actually covers Lot 1) but you'd be insane to dive that spot given that there is no better diving there than at other sites in the park which have much easier access. Parking lots 2, 3 and 4 as you go around the point all offer great dives. Parking lot 2 is on the west side of the point, 3 and 4 are on the east side which means depending on the direction of the seas lot 2 might be divable when 3 and 4 aren't and vice versa.
Parking lot 2 has a fairly steep climb down down some rocks to a cove and a cobble beach, this beach often covered at high tide. You can then enter and exit from the shelter of the cove but be warned that the cove can be a little tricky to spot along the shore coming back if you aren't familiar with the site because the whole shore tends to blend together. Once you get out there are lots of canyons, boulders and a few swim throughs, though you may need to look around a bit to find them. The best diving is to be had between about 15 and 40 ft although you can go deeper.
Parking lot 3 is similar, except that you have to enter directly from the rocks and there is no nice sheltered cove so you are more exposed to the surf on entry/exit. Also the walk down the rocks, while not as steep as lot 2, is longer, and there are plenty of slippery spots so you have to be careful. The rocks drop down to about 50-60ft after which it basically turns into a moonscape along a barren bottom so you won't want to venture beyond this. Most of the swim throughs and canyons are in the 15-40ft range as in lot 2 and there s a really nice one starting in about 20 ftish near where that metal post sticks out from the rocks on the shore.
Lot 4 is much like lot 2 entry wise. There are a couple of big ship anchors here. If memory serves you can find one of them by following the 55 ft contour to the north from the entry, but it has been a while and I don't have my logbook handy for the exact info. Often times you see the chain before you see the anchor, though it is heavily encrusted so it may take you a second to recognize that you are looking at a chain.
If you do lot 3 or 4 there is more than one place you can enter or exit but be sure to scout it out in advance so that you know what you are looking for one the way out. Also as I said before, seen from the water the shore tends to blend together so I would HIGHLY recommend mooring a flag at your intended exit location as a reference point.
