From the air, the flat, small island of Tongatapu doesn't look much like land at all, with the astonishingly blue Pacific Ocean dominating the view.
But it is home to Tonga's capital, Nuku'alofa, and to the majority of the country's population - 70,000 or so out of around 90,000.
And for Tongans - who have lived here since the 9th Century, when the first settlers arrived by boat, the issue of rising sea levels and climate change is not just one for discussion at an abstract level - it proves a threat to their very existence.