The Energy Observer catamaran, claimed to be the world's first hydrogen vessel, has moored on the Thames. It's the last stop on the environmentally friendly boat's 2019 tour of northern Europe. It has sailed around 18,000 nautical miles since leaving Saint-Malo, France in 2017. It toured 25 different countries, propelled solely by electricity. The 30-meter Energy Observer doesn't emit CO2, fine particles or even make noise. It is claimed to be the first vessel in the world that's capable of producing its own hydrogen onboard when renewable energy sources aren't available.