I have flown over the ocean a couple of times so far and I try and stay at least 15 or 20 feet off the water, I'm always afraid of a ? wanting to playing with my drone.?
I have never had an issue 20 feet or above. Although the sensor on the bottom can still measure higher. As to no worries, I would not go that far. I would call it being aware. Keep the bird in sight and 20 feet will give you plenty of time to respond. Over water I have only seen issues down low with very clear water.