Another possibility is to use a fish finder on the cat. I had it on a motor boat I owned. The unit is a Lowrence LMS 520C and it has a gorgeous colour display and has a GPS. The display of the bottom of the lake and the depth is awesome and it takes the worry out of travelling.

This would take a bit of engineering for the probe and mounting the head unit, but after wiping out a set of daggerboards, I am a trifle paranoid bout going to new areas.