Fred, a freind of mine with a 36 ft cruising cat has had a set of those little uhf radios for a couple of years and they are great for that purpose eg sending kids ashore in the dingy or when a fixed vhf is a little too 'fixed' for the purpose. I'm not sure how they would handle a dunking or if they'd get wrecked in use on a beach cat but by the prices they'd be pretty expendable anyway. For reference my friends set gets about 3-4 km across water not 6-7 miles and reception is worse over land
Cheers Phil