It's a little dated... and a big file but check out Chapter 4 Boating accidents stats. Biggest cause... human error, careless operation and drunk boaters.
http://www.bts.gov/publications/mari...pdf/entire.pdf
Sadly, no laws passed will solve the biggest problem(s). Captain Boanhead and Captain Tipsy.
I have to come down on the side of more enforcement and stiifer fines as opposed to more rules. Maybe we need to make it VERY expensive to get out on the lake if you aren't willing to do so safely within the rules that already exist.