I'm up Bridgeport way in CT. Here are some things to think about:
Visibility: Lets just say the Sound is not the Caribbean, The diving in the central sound area can have some better visibility, but the magic temperature number is 45F. Below that and the plankton drop out and the vis opens up. Above and it drops down towards zero by late summer. There have been times off of Milford in the spring when I have seen close to 20' of vis and by late summer we are in 1' or less. A lot will also depend on rain related runoff coming down the rivers. No matter what you should be comfortable as a solo diver and buddy contact can not be assured at any time due to the limited visibility.
You should always be ready for mono, nets, and lobster pot lines to get tangled in. Have at least 2 knifes and be ready to cut your way out if needed. You should also be ready to take you gear off on the bottom to clear an entanglement and then put it back on.
Currents: One of the main things is to dive the tide and currents. I don't even try some places on a spring tide, especially near the Race of anywhere West of Execution Rocks. Get a copy of the tide tables and see when you want to hit a particular area. I like to go just after slack so that there is a bit of current to move the stirred up silt away from you. If you are at slack, it will just hang around you.
Depth: For depths, the sound will rang from flat mud/silt bottoms which can extend a few miles out in the 15-35' range up on the CT side between Bridgeport to East of New Haven to about 150' in the channel on the Southern side near Middle Ground and Port Jefferson. The deepest areas are over near the Race where it gets to below 330' in some holes.
Temperature: Temp wise, the winter will see temps down into the 30s and the summer can see surface temps into the high 70s. I use a wet suit in July, august, and the 1st half of September.
Wrecks: Lets just say there are a lot of them, but you need some info and a good boat and bottom sounder to find them. In the area between Stamford and Eaton's Neck and around Anchor and Cable reef NOAA has charted over 200 wrecks. Most are old barges and such which were scuttled to get rid of them, but there are some better. One is the 'Benj F Packard' which is a 250' long full rigged ship which was scuttled in 1939. She is in 190' and the deck is at 160 or so. Out at the Race, the Volund is popular and at 60 to 100 feet and fairly open vis not bad to start with.
Boat access, there are some State boat ramps that can be used, but you sometimes just have to know where they are. Commercial dive boats are limited and I only know of the two boats out of Orbit in Bridgeport, Atlantis out of New London, Captain Sam may still run out of Stamford and the Sea Turtle runs out of Montauk and will do wrecks in the Sound.