I've been trying to find a a few plastic containers (of different sizes) where the lid stays put and where the container will not leak (let in water), even after being knocked around. I tested (very unscientifically) a number of "Lock & Lock" and "Tupperware" containers that were in good condition that my wife and I had picked up at yard sales. I'm not concerned with liquids leaking out, only that they keep water out and the contents dry.

I was surprised to find that most all of the containers did not keep water out when I dunked them in a bucket of water. Also, I tried kicking them around a little (sometimes a lot) with them half full of water to see if the lids would stay on to the end that the container would still be liquid tight.

What I found indicated that no matter what the plastic containers looked like, the information from the manufacturer's website seems to be the best guide as to whether a particular container series is waterproof (liquid-tight). All the ones that leaked were containers that the manufacturer never claimed to be liquid tight. Containers that are just "air-tight", always leaked (with one exception). In other words, if you need a plastic container that will keep critical items dry no matter what, make sure the container's packaging label says, for instance, "liquid-tight" (or words to that effect).

The one exception that I found was a small Tupperware container from the "modular" series. The website does not state it is waterproof, yet I left it underwater for an hour and it did not leak. Also the lid did not come unsealed when I filled it halfway up with water and kicked it around.

As to Lock & Lock, the only ones that the literature indicates are liquid tight are the ones from their "classic" series. From Tupperware, it's the "Pak-N-Store" series.