Meet the FT Sea Otter: a DIY water plane made from a water-resistant foam board that can move over water and fly in the air. The kit includes almost every component you need to build your own plane. You can optionally get a Lumenier 2250mAh 3s 35c Lipo Battery for it. The below video shows how the FT Sea Otter works:
The above video shows this seaplane in action.