Here is the video I made last weekend over water. I took the Phantom 3 pretty far from the boat and had no problems.
But another guy from another boat was flying a Phantom 3 Professional and the worst thing happened!!. It was about 50ft up filming people in the water and suddenly the Phantom powered off and crashed like a rock in the water. MY HEART STOPED for a moment even that it was not my drone!! When the guy jumped in the water to retrieve it, he came back up with the drone in one hand and the battery on the other. So I guess the battery got loose and shut down the drone. I don't know if this has happened to anyone. After this incident I decided to ground my drone, didn't want to have the same experience of that dude!