I certainly can't make any kind of "certifiable" claims of waterproof-ness, IP66, IP67, etc. However, I've taken every precaution possible, to ensure that heavy rain is not going to cause a problem for these lights. I feel pretty comfortable calling them "dunk" proof, but I wouldn't want to go so far as to say that you could use them under water.

http://www.youtube.com/watch?v=zsrSh5veYZk