I ran my boat out of Alpena for 15 years. That was a long time ago, but I'm sure they are all still there. Our number 1 favorite was the Monrovia a salty that was sunk in a collision in the 50's. It sits upright and intact in 150 ft of water. Top of main superstructure is 80' Main deck is 110' from front of the main superstructure forward. Its 100' from rear of the main superstructure to the stern. It's tore up at the hold between the main superstructure and the engine room superstructure. That's where she took the collision. Also there's damage that was done there by blasting to clear the wreckage so the steel she was carrying could be salvaged. She's fully intact from there back. The boiler and engine rooms are really cool but its around 135' in the bottom level. She is a fantastic dive. Only problem is she is 25 miles out from Alpena, 13.5 miles due east of Thunder Bay Island light house. Whoever you are diving with may not want to make the long run out there.
Closer in there is the Grecian, another nice dive, she's only three miles out of the mouth of the Bay. She's in 105' ft of water, 80' on the deck. All the structure above deck was wood and is gone. The bow and stern are intact, the center section collapsed. The engine room is about 95' its interesting but it gets tight in places. The steerage gear in the stern is interesting also. Inside the mouth of the harbor in about 80' is the Montana an old wooden steamer that burnt and sank. Interesting artifacts and the steam engine towers up about 30' off the bottom, an impressive sight on a good visibility day. The Van Valkenburg, an old, fairly intact schooner is also inside the mouth of the Bay in about 70' of water. If the weather is bad and you are a little hard up there is the Monohansett in 25' of water near Thunderbay Island. There are some other good dives like the Viator and Pewabic but they are out in 180-190' ft of water. There are a number of good wrecks in the area, like the Norman (a sister ship to the Grecian!) found since I quit diving up there but they are a long run North of the Bay and are in very deep water. By now they may have also found some more good dives in shallower water, you will have to ask the locals about that. Have fun!