Arduboat self bait drop

I am totally new in apm and i need some help.
I want to make a fishing boat controlled with apm . I have the APM 2.8… and i need help how i can set it up.The most important thing is that i want from my apm when the signal is lost and the RTH function is self armed ,at the same moment to operate a servo to drop my fishing line and not bringing it back to me.Is there a code/diagramm/e.t.c ?
Best regards

Everything you need is here:

Spend some time reading through it and it should answer your questions.

Thanks, Grant.