Dropping a GoPro down a well

Our well drilling report from Barney Moravec mentioned that there were caves in the limestone at 110'. What could that possibly mean? We sent down a GoPro to find out.

FORMATION 1: 0-53' SAND TILL & GRAVEL
FORMATION 2: 53-110' LIMESTONE - CAVES AT 110'
FORMATION 3: 110-120' LIMESTONE