By the way, as mentioned here, the people at BlueRobotics tried to send a solar powered BlueBoat from California to Hawaii and in 2.5 days it travelled 127km before it flipped (see mission result here).
I’m not trying to divert people to getting a BlueBoat but just providing some encouragement because we’ve now had at least one official attempt to cross an ocean using ArduPilot. With the right hardware, I’m sure it can be done.