Good one Sam, just keep pressing the buttons to discover what they do, Navionics is quite intuitive. Keep pressing buttons you cant break it.
If you haven't discovered yet (what I think is the funnest feature, also the simplest) is simply press "Start" when you start your journey, then press "Stop" at the end of the day. It leaves a yellow line along your track & you can review your journey, your tacking into the wind angle, where your hat blow off & you had to turn around and get it (MOB drill) etc
cheers