I've been using my Mavic to film wakesports on a moving boat.  The problem I am having is half way through the flight the bird wants to stop and return to home point it recorded when I launched from the boat.  In my case there is no home point to return to.  I can cancel the request, but my worry is that one of these times it will take off and head for home and land in a watery grave before I can reach it.  Any work around for this issue?

You can set up RTH to your current position. It will use your phone GPS location.

You can set it to hover too instead.

Set the RC as homepoint in the App

Lok Mavic Posted at 2017-5-30 12:57
You can set up RTH to your current position. It will use your phone GPS location.

However it is not dynamically updated. This means it will be of  limited use on a moving boat.

So reset home point to you (on boat), boat moves and Mavic lands in water at the point where you last updated home point to.

The Litchi app has a true dynamic homepoint feature that continually updates the homepoint as you move.  

Logger Posted at 2017-5-30 16:51
However it is not dynamically updated. This means it will be of  limited use on a moving boat.

So reset home point to you (on boat), boat moves and Mavic lands in water at the point where you last updated home point to.

Unfortunately, only Inspire supported by DJI Go 4 for that function. They can bring it to other devices to but I doubt it will happen soon. Just that is the closest alternative apart from spending £20 on an app.

If your Mavic is requesting to RTH while your RC is still connected, that's the Smart Return Home feature wanting to make sure it can get back home with the remaining battery. You can disable this in the battery section of the options.

Also, if you haven't already, you probably want to change the Signal Loss behavior. The default is RTH, but you would want it set to hover.

And as Logger stated, the Mavic doesn't support a dynamic Home Point.