Problem is even if there is safe ice on most of the water you have areas that are thinner.
We had 2 high school kids go through the ice across the street from my house a few nights ago. The ice must have been pretty safe as there was people on it for a few days. But these 2 were just walking around and through it they went.
The guy got out but couldn't get the girl out. He got help ASAP. I guess she held on to the edge of the ice.
The first patrol unit to arrive went out and reached her with a hockey stick. That was enough for him to pull her up onto the ice and grab her. [up]
Trajedy avoided, but barely. It only takes one small area to start going and it just escalates.