The boat design is 2 layers of plastic with foam between the layers. Top part of the boat is connected to the bottom with the "rub rail" that goes around the boat (top and bottom half are sandwiched together there). No seams under the water line = no potential leaks. The top half of the boat is the inside, and the bottom is the outside.
As light as it is, it's very easy to tip on it's side to get the water out, or bail it out. I'm still very happy with it.
