I recommend that you start from a dock with some short flights over water coming back to the dock. Then move to a boat that is moving under power so that it can be stopped if you are having trouble recovering the drone. If the boat is moving, ALWAYS fly from the back of the boat (so when you let go of the controls, the aircraft goes to a hover and separates from the boat). Gradually increase the winds you fly in. Always have a helper who has no other responsibly on the boat to catch the drone while you fly. The obstacle sensors make the drone not want to get close enough to the boat to recover, so I get the drone close and then turn it around and converge to the boat backwards. Almost easier to fly the drone that way (left stick moves the drone left...), but you can't use the camera view. There are a number of settings that you definitely want to set such as automatically updating the home point and disabling max distance setting. Shutting the drone down is also a challenge since the drone does not recognize that it has landed and is frantically trying to hold position. Usually just turning the drone 90 deg onto its side does the trick (I also keep full down on the throttle). Once or twice that did not work but when I held my hand under the ultrasonic sensors on the bottom coupled with the full down throttle the drone shut down. Heavy gloves is not a bad thing to have on. The blades are very nasty if they hit your fingers.
When I first take off, the drone just starts climbing and it takes a few seconds of holding the down throttle to make it stop. Not sure what is happening, I suspect that the catching handle is interfering with the down sensors. After I make it stop climbing the drone flies normally although I never trust the altitude hold or altitude readings.
It always is a bit nerve racking, and there are no guarantees. If the aircraft sheds a propeller blade or something while over the water, then your drone and the video you just took are gone. There are floats and similar things you could use but I am more worried about adding even more stuff to the drone and messing up the flight behavior and I don't trust that they won't just break off the drone if it crashes in the water. Unless you have insurance, recovering the drone out of the water is useless anyhow, it will still be ruined. Same is true for losing a propeller while over the ground.
BTW this is the other mount for a handle I was looking at.
DJi Mavic Pro & Platinum Bottom Mount 4.0 by jeanmariecannie on Shapeways. The link did not work in my last post (mount is expensive ($30 plus $10 shipping). Your mount looks like it should work great.
