I make myself super obvious if doing something within a neighborhood. I have flagging tape to keep people away from the landing site, I use a spotter. I have the goofy FAA certified pilot vest LOL, And I have a tiny "information" stand with a...
After 10,000 miles flying over water, I can confidently say that's just not true.
Your drone will fly over water just as it flies over solid ground.
What's down below makes no difference to the drone.