Let's take paddleboarding as an example. It's important to note that paddleboarding is the equivalent of BIXI biking on rivers and lakes. It's an extremely accessible activity, and it's becoming increasingly widespread. Regulations must set limits on boating speed, indeed, but they must also define separate reserved areas for swimmers, for low-wake craft, and for large motorboats.
This type of regulation exists on public roads, but not on bodies of water. People have the impression that a body of water is not a public highway. So they think it's every man for himself and that the water belongs to everyone.