To be honest, the shallowest (is that a word?) wreck that's recognizable is in 80 feet of water. There is the Sydnee O'Neff (sp) that's in about 15 feet of water and there's the Green Island Wreck that is pretty broken up but those would require a boat/charter (M&M Diving). If you're looking for shore diving there's some pretty interesting stuff behind Perkins (there's a boat launch behind it (advice - DON'T park on the hotel grass, they DON'T like that). I can get you coordinates, there's some carts, and anchor, etc. out there. (some nice freshwater sponges too). The lighthouse makes a real nice shore dive if you're into fishing (fishing gear galore!). It's a pretty easy entry and a nice dive with lots of fish. It's pretty cool to to around to the entrance of the river and watch it flow over you (your gear will stink afterwards). The bass will follow you around. If you have a boat, there's a couple of other spots that I can give you where there's log piles, anchors, etc. Lot of junk including bottles, etc. Let me know.
One more thing... The Bay is never consistent with viz. One day you could have 30 feet and the next day it could be less than 2'.