The vessel "Energy Observer" is docked at Flisvos Marina in Athens, Greece, on June 21, 2018. The first vessel powered by renewables and hydrogen, "Energy Observer", has moored at Flisvos Marina in Athens this week in the 20th stopover of its world tour to raise awareness on energy transition and meet pioneers who work for a cleaner planet. (Xinhua/Marios Lolos)

?