Answer:

spelunk

Answer	Crossword Clue
SPELUNK	Go caving
SPELUNK	Participate in some underground movement?
SPELUNK	Explore caves

SPELUNK	Chart caves
SPELUNK	Explore among stalagmites and stalactites
SPELUNK	Cave
SPELUNK	Go below, in a way
SPELUNK	Explore in the dark, perhaps
SPELUNK	Do some underground exploring