The first is wakeboarding in a cave in Lebanon by Red Bull.
http://www.youtube.com/watch?v=vts9HZsO2OM
I have no idea what they used to pull him through the cave, but it is pretty cool stuff.
And this really isn't a video clip, but a very cool site of the winds of the world.
http://earth.nullschool.net/
And here is a video of a cave dive looking to find a way on
http://vimeo.com/m/82260291
I've got more, just no time to find them all right now..
Enjoy the links.