http://youtu.be/MwgKg1OouUA
The above video is Chasm, where we were able to get under the level. The entire area under the level is a massive water hole, and you can swim around under and outside the level. As far as I know we are the first to find these glitches in the new levels. All of this was done on unmodified versions of the game, most recent patches.
We were able to achieve a similar effect on Prism as well. However Prism was much more difficult and I was only able to get my friend in. We are going to try again later and if I am able to get in I will put up a video of that as well.
DISCLOSURES: I do not condone the usage of cheats or glitches in true multiplayer matches. If such a thing becomes widely used it can truly break a game and otherwise fun levels. (I'm thinking of multiple instances on MW2 maps). These tests were done in Private Matches, however feasibly it could be done in a multi match. I did not include how to do the glitch as I don't want to see a bunch of n00bs under the level every time I play. If you have an interest in seeing how it is done, I will show you if I consider you trustworthy. (In other words, you probably need to be on my friend's list or at least played quite a few games with me.)