In chicago, we usually drink on my boat. I dont bring a ton of people on board, maybe 4 tops, and we stay low key. We usually anchor and sip some beers in the sun. I think the water cops are more prone to stopping a boat loaded with people, especially if its a sausage fest boat. I dont let people sit anywhere but the seats while underway. Point is, here, if you done act like a asshat, they usually let you enjoy the day.
I have a couple friends who are chicago marine police, they are pretty good guys, who dont want to put the screws to decent people. But if they see a group of people on a boat being rowdy, speeding in crowded areas, drinking out of plastic cups, hanging off the back of the boat while underway, they will stop them.