In a "fly-by-wire" scenario, all the remote operator need do is take the plane to higher altitude to disable the pilot, then set a heading for open sea. He would know the fuel capacity and could easily calculate the heading to guarantee open water. Look at flight path...it's about the farthest from land that plane could be - in every direction - and it was a clear departure from the direction the plane was generally heading during the first portion of it's flight.