Agreed -- Winnipesaukee is a fun place to dive...if you know where to go. Granted, most of the wrecks are smaller and older, but there's plenty to see in 70 sq miles of Lake. Depths to 213' -- abundant aquatic life.
Dive Winnipesaukee in Wolfeboro (eastern side) has a shop, and a boat docked right behind the shop. I dive with these guys regularly, and it's always a good time. The Diamond Island Navy SCRIPTS test site is a fun dive -- with the nearby "Empty Pockets" wreck. I just revisited it on Sunday. Numerous artifacts can be found -- primarily near the big islands with the older homes on the western side of the Lake. If you like old bottles, pottery, and boats, there's something there for you. Granted, it's cold, dark and murky below 40 feet, but it's certainly worth checking out if you're in the area!
The folks at Dive Winnipesaukee are MOST helpful and knowledgeable. 603-569-8080.
On the other (western) side of the Lake, Fathom Divers also runs charters and is staffed by a very astute team of professionals.