That limits your choices. A few of the Family Radio units are pretty durable. The Motorola Talkabout 6300 ($90) would be a good choice, and you can always put it in a heavy-duty freezer bag to give it some waterproofness. These units have obvious limitations in terms of range, but they're pretty good for use around camp or when out on the water. They won't reach over a mountaintop, but then neither will more powerful radios without a repeater or some other device that can intercept the signal and forward it to the next station. So my advice would be to get pair of FRS radios, live with the shortcomings, and call it good. Somehow we all got by for years without ANYTHING like this, so I think you'll find a FreeTalk or Talkabout a suitable device.
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