If you plan to spelunk in caves without modern amenities, bring a headlamp and a flashlight with extra batteries.
Word Origin and History for spelunk
n.
"cave, cavern," c.1300, from Old French spelonque or directly from Latin spelunca "a cave, cavern, grotto," from Greek spelynx (genitive spelyngos). An adjective, speluncar "of a cave" is recorded from 1855.