I have a Mavic Pro. It is a great drone. I have found that hand catching it is really the easiest way to land. I have made a few nice videos of slow sailing days and a couple scenic videos on Seneca Lake as well as a video of my 16 ft center console on the lake. We got lots of good angles and altitudes.
As far as keeping track of the drone from a moving boat, there is a return track on the map inset and two “Return To...” modes: Return to Home (takeoff point) and Return to “You” (where the controller is). If you fly out of sight, you can fly back down the return track on the map inset. However, if the boat has moved, your default return track will not bring you back over your boat, but to the gps coordinate from which you took off. You can change this to track the controller, so you always return to a position over where you are.
If you forget this, there will be a tense moment in which you think the drone should be overhead, but you do not see it.
The “Return To...” functions relate to the “RTH” button on the screen and controller. Pressing the button will cause the drone to activate a prescribed climb, a turn, and a flight back to “home,” which defaults to a gps takeoff location. It is very accurate, like within inches in my experience.
Additionally, using a launch / landing pad helps the drone find its exact takeoff point for landing. The drone actually takes a picture of the spot from which it took off, so giving it a few moments to hover after takeoff is smart, although not necessarily an option on a boat.