The world's largest cruise ship has set sail on its maiden voyage from Miami, Florida, raising concerns about its methane emissions.
The 365 m (1,197 ft) long Icon of the Seas has 20 decks and can accommodate up to 7,600 passengers. It is owned by Royal Caribbean Group.
The ship will embark on a seven-day voyage around the Caribbean islands.
Environmentalists have warned that ships powered by liquefied natural gas (LNG) leak harmful methane into the atmosphere.
Built at a shipyard in Turku, Finland, this Bahamian-registered vessel features seven swimming pools and six water slides.
It cost $2 billion (£1.6 billion) to build and will also include more than 40 restaurants, bars and lounges.
Although LNG burns cleaner than traditional marine fuels such as heavy oil, there is a risk that some of the gas may leak and methane leaks into the atmosphere.
Methane is a much more potent greenhouse gas than carbon dioxide.
“This is a step in the wrong direction,” Brian Comer, director of ocean programs at the International Council on Clean Transport (ICCT), said, according to Reuters.
“We estimate that the use of LNG as a marine fuel results in more than 120% more lifecycle greenhouse gas emissions than marine diesel oil,” he said.
Earlier this week, ICCT released a report claiming that methane emissions from LNG-fueled ships are higher than expected under current regulations.
Methane, a powerful greenhouse gas in the atmosphere, traps 80 times more heat than carbon dioxide over 20 years. Reducing these emissions is considered important to slowing global warming.
Royal Caribbean says Icon of the Seas is 24% more energy efficient than the International Maritime Organization requires for modern vessels. The company plans to introduce net-zero ships by 2035.
The cruise industry is one of the fastest growing sectors of tourism, with young people particularly interested in cruise travel, according to the Cruise Lines International Association, an industry group.
The cruise industry contributed $75bn (£59bn) to the global economy in 2021, the report said.
On Thursday, Argentina's World Cup-winning captain Lionel Messi, who currently plays for Inter Miami, took part in the ship's naming ceremony. He was seen placing a soccer ball on a specially constructed stand and triggering the traditional “good luck” champagne bottle smashing motion against the bow of the boat.