On Tuesday 28 May, The King went on board the world's first hydrogen-powered boat, the Energy Observer catamaran, which was visiting Stockholm.
The Energy Observer is touring the world to investigate, develop and promote future renewable energy forms. The vessel produces hydrogen gas from seawater while it travels, and does not emit any greenhouse gases or airborne particles.
During his visit, The King was given a tour of the vessel by the project's founders, Captain Victorien Erussard and expedition leader Jérôme Delafosse. The King also visited the exhibition about the expedition which was on display near the boat.
The Energy Observer is carrying out a six-year world tour to demonstrate its entirely emission-free technology. The tour called at Stockholm, mooring at Logårdstrappan, Skeppsbron 2, until 2 June.
The Energy Observer's exhibition, including VR and filmed material from the expedition, was displayed alongside the boat. The free exhibition was open to the public.
Find out more about the Energy Observer here.