You're looking for a camo-covered wide mouth Nalgene bottle that is big enough to hold a lot of small tradeables. The cache is only visible from a certain angle so you'll know it when you see it. 
Please be sure to seal it properly and place it back in the same spot you found it. Wouldn't want it to be part of the wash out now, would we? Initial tradeables are a hand painted Iron Man keychain, a tracker bug, and lots of other small swag.
It would be awesome if you practiced a little CITO while you're here, it's pretty overrun with trash from previous washouts.
Happy hunting!