Hell's Gate [German Import]

A group of spelunkers go down to help out their buddy who's been hanging out in a cave for 78 days as part of some sort of record. During the last hour of his underground incarceration, the record-setter freaks out and starts screaming that someone/thing is trying to kill him - so his buddies decide to try to get him out. A pair of meddling college kids looking for an underground tomb join the group and they all go in search of the missing cave-dweller...