A much better question is "How does the visibility change there between, say, Friday and Sunday?"
Depending on where you go, the viz either doesn't change much (mostly the deep side where a dive plan must be filed at the office) or is affected by the presence of divers who are still working on proper buoyancy and weighting. (Yeah, I could have said new OW classes, but there are
plenty of certified divers of all kinds that stir up the bottom from time to time.)
The viz can be fantastic early on Saturday morning (and by fantastic, I mean 30-50 ft, it is still a quarry) and drop to <10ft by the afternoon. The
Great Lakes Wrecking Crew forum will have lots of posts about Gilboa, but when we have our semi-annual Meet & Greet there, we plan for April and October/November partly to avoid the crowds, but also because there are fewer students to mess up the viz.
-Rob
P.S. Uh, yeah, you already posted in the GLWC section so you're in the right place. That should be a lesson for me when I'm responding to posts from the search results.