The only regulation in Wisconsin states that you cannot operate a watercraft or ski/tube/wakeboard, etc if you are under the influence or have a BAC of .08 or higher. From my experience boating in Wisconsin, everything is pretty relaxed. Just don't do anything stupid.
With that being said, different lakes are patrolled by local municipalities. The lake a live on is small and has one police boat that is only out about 6 days out of the year. He will watch from shore with his boat covered though to see if anyone is doing anything stupid. He stopped me once the day I launched my new to me pontoon because 2 different colored stickers were showing. I had a beer in my cupholder, he just verified it wasn't in a glass container (illegal on many wisconsin lakes so know the rules of each lake), asked how many I had (it was my first one), went through the standard safety check and let me off with a verbal warning for the sticker since all my paperwork was in order and no other infractions.
5 things they look at in Wisconsin: Registration (proof of insurance not currently required), PFDs (under 13 has to be wearing at all times, 1 for each person 13 and older on the boat) Throwables (I always have 2 in the boat since the admiral likes the seat cushion ones) charged fire extinguisher, and covered battery.
Met him on the sandbar later when he was off duty and gave him a beer.
Other lakes are not as forgiving. Like I said, it is up to the municipality to patrol the lake and some lakes are very strict with these types of things. My advice, go to the area where people anchor and party (every lake has one) or a bar on the lake if it has one and talk to the locals.