maybe anchor, but if need be, stay loose to ride up n down. rather than anchoring to the bottom. there is also a bouy marking the wreck, so if it is legal, tie to it.
I cannot speak for that area but usually buoys are placed for tie off to. But, in this particular case I do not know.
Aside from drift diving (which does not really pertain to the Great Lakes) I do not think having the boat free and under power maneuvering in the area while divers are below is a good idea. It is real easy to loose divers in the water and can be even more difficult to find them again. If the weather and conditions are bad enough you cannot anchor then you should not be out there to begin with. Just my thinking on it. I don't like the idea of an inexperienced boater leaving a less experienced boater motoring around the area while divers are in the water (you), to much opportunity for mayhem and disaster.
You better get yourself at least a handheld VHF and GPS. Well, good luck.
N