They are waterproof barrels that are used to transport raw protein. One of my friends got a bunch for us years ago and they work great. Each on probably holds about 90lbs of water. My friends dad uses them for his dry storage when they are canoeing. Filling and emptying is real quick too.
Mike - I have no idead if you can just buy them anywhere.
Byron- don't know exactly what it was but we were wearing shorties and your forearms and hands would get a bit cold after a while. Chilliwack lake is glacier fed so it never gets warm even in summer.
RJ - Yes, at the park. All of these shots are taken down at the far end of the lake.