[CurlyDave]

...It wouldn't be that difficult to fashion a system using a garage door opening system or an inexpensive radio-control toy whereby a person could attach a small transmitter to themselves which could be used in such an emergency to de-activate an autopilot system...

I think making this waterproof against salt water immersion would be difficult, but possible.

Cost might be high.

[William Tell]

CurlyDave said: "I think making this waterproof against salt water immersion would be difficult ..."

The unit might only have to tolerate complete immersion ONCE to pay for itself.

There would be an issue of protecting the unit for its lifetime in the harsh marine environment, where it might get splashed on occasionally. The marine version of some shotguns are made of stainless steel to reduce corrosion.

I'm such a poor swimmer that I wouldn't find myself in the position of being alone at sea in a 36 foot boat. It's a stretch for me to be accompanied by 3000 passengers and crew on a thousand foot cruise liner.

[MV=PY]

"I think making this waterproof against salt water immersion would be difficult, but possible. Cost might be high. "

I'd make it so it's failsafe. Transmit every 10 seconds. If the signal isn't received the motors shut down.