Couple years ago I talked the gal at the Dollar STore into letting me have 4 of theirs, looks like the same one in black.
Nope, not water proof, left one out one summer and found it full of water, they do hold water!
I'm thinking of using these heavy tubs bolted together as a base for a platform. May have to make a wood templet or pieces to take the curve out to screw or bolt them together but it would be lighter than using 2x4s and I know they won't collapse but they could wear down over time I guess.
I'd like to see how others use heavy or light weight containers too, drawer systems, hanging storage and upright cabinets......