Pugh is best known for undertaking the first swim across the North Pole in 2007 to highlight the melting of the Arctic sea ice. In 2010 he swam across a glacial lake on Mount Everest to draw attention to the melting of the glaciers in the Himalayas, and the impact the reduced water supply will have on peace in the region. In 2018 he swam the full length of the English Channel to call for 30% of the world's oceans to be protected by 2030.