Jakub Bures and Jan Kara are two friends who are gravely concerned about pollution of the waterways and oceans of the world, specifically plastic bottle pollution. So rather than just sit and worry about it, they decided to do something to highlight the issue. They built a water-going boat from more than 50,000 plastic bottles filled with dry ice to aid buoyancy! And you know what? It floated! So they set sail down the Elbe River from Nymburk in the Czech Republic to Hamburg, Germany, a total distance of 530 miles.