I practiced with a unicycle quite a bit 20 or so years ago and I'm just not a fan. Found it uncomfortable and tiring. You can't relax on a unicycle and glide somewhere. It's no faster than walking or jogging. And as far as exercise goes, the constant back and forth and twisting on a unicycle puts quite a bit of strain on your core body muscles -- you get a workout but a jarring workout. I really found little to like about unicycling apart from the thrill in seeing people's reaction and the satisfaction of learning to do something difficult. In a cave, well I understand the allure of the technical challenge. But I've been in a lot of caves also and they're just not very enjoyable places, not without a lot of light in any case. So in my book, unicycle + cave sounds like one of the worst ways to spend an afternoon!