Having been a Scout leader for a while, and seeing what boys can do to hard-sided water carriers and how short a lifespan the carriers typically have, the exterior wall of that thing had better be darn thick to avoid punctures.

The funny thing is that is exactly why ships used to carry stuff in barrels. They were easy to roll. The only difference is that barrels had what in canoe terms is heavy "rocker" (wider in the middle than the ends) so that the barrel can easily be turned or "bounced" upright.