what settings for return to home if you are on a ship?
i want to take off my drone from boat in moving and what settings to apply to not landing the drone on the water.

There are no settings for RTH.
There are settings for Loss of Signal which include RTH, Hover or Land.
If you are on a moving boat, that won't turn around and go back, you do not want to set Hover.
You don't want to set Land.
That leaves the default setting , which is RTH.

But you will have to be careful if you are on a moving boat because you don't want tour Phantom to land where it was launched if the boat has moved on.
You don't really want the drone to land on the boat anyway, even if it is in the same place.
You will have to hand catch to avoid compass issues landing on a steel boat.

You will also have to be careful because as the Phantom gets further away from where it was launched, it will want to return when it calculates the battery level is getting low for the return to where it was launched.
You can reset the homepoint during the flight to prevent this.

You need to have experience on land with all the special things needed for flying on a boat.
It is an unforgiving environment and not a place to be learning.
Just one mistake and you could be going home with one less drone.