They told him they were going bungee jumping

The terror he must've felt as soon as he hit the water...good thing his pants were already wet.

I don't get it.... an optical illusion?

1. He's one brave motherfucker
2. He has some shitty friends

Best prank ever!
Though who would want to go bungee jumping blindfolded?

He's probably pledging into a fraternity.

My guess is they put all the pledges in that truck in the background, drove up a mountain and told them they'd be bungee jumping from a cliff. They're keeping the pledges in the truck so they can't hear or see anything. Then one by one, they bring them out to the platform and tell them to jump off of the "cliff", which is really just a lake on a mountain. See who is loyal and committed.