GPS Module
Waterproof Transducer
Glue half of a large bubble float to the bottom of the boat with a small standard camera module inside and drill a hole in the hull for the wiring?
Motor and servo, a microcontroller and a big battery to run it all
Put together your controller, mount your sensors and modules on the boat, write up the code, draw flowcharts etc
When you have actually done that, someone here will perhaps help you get it working the way you want, until then Google is your friend...
rgds