It's not just boats that have safety-critical UI design problems. The avionics in airplanes are becoming so complicated that managing the avionics is almost more difficult than flying the plane.
I'm a private pilot who has been flying a Cirrus SR22 for twelve years. In that time it has gone through two major glass cockpit avionics revisions. In the first revision, called the Avidyne, the autopilot was either on or off. In the current revision, called the G-1000, the autopilot can operate in two modes: AP mode, where the autopilot is actually flying the plane, and FD or flight-director mode, where the autopilot does all of the calculations to figure out where the plane should be flying and displays a target on the primary flight display, but the actual control of the plane is still in the hands of the pilot.
If the plane is stable, it is very easy to get fooled into thinking the autopilot is flying the plane when in fact it is not. There are only two visual indicators that tell you if the autopilot is actually flying the plane: a small green LED on the autopilot console, which is down near your right knee, and another small annunciator on the primary flight display. It looks like this:
http://is3.mzstatic.com/image/thumb/Purple71/v4/9a/36/ad/9a3...
The autopilot indicator is indicating AP mode in that image. See if you can spot it.
It has happened to me more than once that I thought I had the autopilot engaged when in fact I had only turned on the flight director. I predict that one of these days someone will die because they made this mistake in instrument conditions.
