There are tons of things that are fun if you do them but if a lot of people do them ruin something or other. It's called the tragedy of the commons: http://en.wikipedia.org/wiki/Tragedy_of_…
In this case, the shared resource is the natural beauty, peace, quiet and tranquility that a natural body of water affords. If one person jet skis once a year, probably not a huge deal. When lots of people do it, it ruins everything for everyone.
Noise pollution is kind of an abstract concept that a lot of people don't really fully grasp since it's hard to think of quiet - the absence of something - as a shared resource.
And I fucking hate leaf blowers with a passion too.