According to Defense-aerospace.com, China’s first large amphibious aircraft AG600 on December 24, 2017 completed its maiden flight in south China’s Guangdong Province.

At 9:39 a.m., the aircraft AG600, code named «Kunlong» left Jinwan airport in the city of Zhuhai. The flight lasted about one hour.
«The maiden flight makes China among the few countries capable of developing a large amphibious aircraft», said Huang Lingcai, chief designer of AG600.
The Communist Party of China (CPC) Central Committee and the State Council congratulated all those engaged in the mission, including those from the Ministry of Industry and Information, the Civil Aviation Administration of China and the Aviation Industry Corporation of China.
The congratulatory message said that the maiden flight was a major breakthrough in developing special-purpose aircraft following the maiden flight of the large C919 passenger jet in May.
The 39.6-meter/130-foot aircraft is powered by four domestically-built turboprop engines, according to its developer, the Aviation Industry Corporation of China (AVIC).
With a maximum take-off weight of 53.5 tonnes/117,947 lbs and a top cruising speed of 500 kilometers per hour/311 miles per hour/270 knots, the AG600 has a range of 12 hours.
Designed to be the world’s largest amphibious aircraft, the AG600 will be mainly used for maritime rescue, fighting forest fires and marine monitoring.
It can carry 50 people during search-and-rescue missions, collect 12 tonnes/26,455.5 lbs of water in 20 seconds for fire-fighting and transport up to 370 tonnes/815,710 lbs of water on a single tank of fuel.
Its name «Kunlong» stands for a high expectation in Chinese culture with the «Kun» meaning an enormous legendary fish and «Long» a dragon.
The AG600 is the third member of China’s «large aircraft family» following the large freighter Y-20 and large passenger aircraft C919, which made maiden flights in 2013 and 2017. The Y-20 entered into service with China’s air force in July 2016.
“Designed to be the world’s largest amphibious aircraft”
Yeah, China keeps saying that but it’s complete crap. There are several that were much larger than this thing. This for one:
https://www.youtube.com/watch?v=mrdLJ3GYVac
this for another:
https://www.youtube.com/watch?v=QowTqmxYZ1Q