I drilled a hole off Tyranena Park earlier today - 3 inches just a little off the shore. I didn't venture out much further by myself after that.
I'm guessing there is a shelf of 3 inches that includes stuff that was frozen earlier in the week near the park. Not too far out, though, just froze over so I'd guess that is not quite as thick.
People were fishing on in the marsh last week, so I'd guess that is at least 3 inches if not more right now.