I have to say Great Lakes especially the north shore of Lake Superior. It is cold water diving, but the wrecks are totally intact. I dove one that was a wooden sailing schooner. It was built in 1869, sank in 1896, I dove in in 2006, and the paint is still on the oak deck. Try to duplicate that in any saltwater. The vis on north shore is about 100 ft. The water is so clean and cold and pristine that the shipwrecks are like totally moth-balled, totally preserved. Try diving the "American" off Isle Royale. The exposed pistons in the steam engine... I am 6 ft tall and when I spread eagled on the top of the piston I could not touch the sides.. HUGE pistons. Or dive the Madiera, near Split Rock Lighthouse, near Two harbors, Minnesota ... 430 ft steel hull, sank in 1905 in 35 foot waves (on a lake) and the bow is pointing up. When you approach it it looks like a cathedral. Tip of the bow only 40 ft deep, stearn about 110 ft. Spectacular vis.