I liked the ambiance that the lighting and sound design gave.
I didn't like how long it took to get to the good part; basically the driving to the cave and walking through most of the cave was dull. Give me more things to do / learn on the way to the main event.
It definitely got me pretty scared (granted I get unsettled pretty easily). I hate to admit that I had to psych myself up to jump into the hole at the end. Overall, pretty good entry, great work. I hope you get your 20 by the deadline.