It's nothing new. Civil engineers at universities have been building and competing in the cement boat challenges for many years now. It's right up there with the robot competitions, alcohol cars and the mini baja and formula racers.

Cement boats themselves have been around for years as well. Being built as others have noted, slathered over chickenwire, sometimes smoothed out with female moulds. There's a number of them around me here in the bay. They seem to work well enough. I understand repairs are just about impossible though.

The light weight canoes built by CE students are purpose built, and would never survive real world use. They are designed to barely survive the challenge of the race. One that could survive would have to weigh more. If you really are interested in it, I'd suggest contacting the CE department at your local or nearest university. There's a whole world of strange and unusual cements out there to play with.