Located around 3km from Hyop-Hyopan Cave, the more challenging Calabidongan Cave (literally, Cave of the Bats) is for more adventurous, confident spelunkers as its partially flooded interior requires you to swim a short distance within the cave. It can only be accessed when water levels allow (typically from March to June) and it's a really good idea to bring a waterproof torch. Guides at Hyop-Hyopan can arrange transport; exploration of Calabidongan's subterranean depths takes a couple of hours.
