Coach writes on floor

This may sound crazy, but I would make sure the coach does wipe it off before any action. The dry erase stuff can become slippery if someone were to step on it. Sounds crazy, yes, but I've seen it happen when I was a coach. After that, our game administration always told opposing coaches to not write on the floor with either dry erase or chalk. If they asked why, our AD used the example we had.