Caves may be remote, hidden at the end of a difficult trek. Several of the caves Cheeptham investigates are deep in grizzly bear country, so the scientists have to be carried in by helicopter. While some caves are roomy, plenty of others are full of tight squeezes and difficult to navigate. Sometimes there are ponds to cross, which can be vast. On one occasion, Cheeptham sent a diver to scout a watery cave and he reported that, if drained, the pond he'd paddled through might be three times the size of BC Place, a stadium in Vancouver that can seat more than 50,000 people. There are caves that can only be explored in winter, when some of the water freezes. And then there is the pitch-blackness, punctuated only by the glow of headlamps. "Every time I go down there I have to basically shut off my brain," Cheeptham says. "I've never seen any horror movies related to caves…if I watch those I might not be able to go."