Cruise Lines International Association (CLIA) has released its 2025 Environmental Technologies and Practices (ETP) report, covering the oceangoing cruise industry and showing measurable advances across its member fleet, which accounts for more than 90% of global cruise capacity.
The report details the profile of CLIA members as of August 2025: forty-five ocean-going cruise lines operate 310 ships and offer 637,847 lower berths, slightly different from the previous year’s 303 ships and 645,034 lower berths.
It projects that through the order book, which runs through December 2036, the proportions of ship sizes will remain relatively balanced. Vessels with fewer than 1,000 lower berths will comprise about one-third of the fleet; those between 1,000 and 3,000 lower berths will remain a plurality; large ships (over 3,000 lower berths) will increase modestly.
CLIA’s analyses show growing adoption of multi-fuel capable engines that allow ships to switch between conventional marine fuels and zero- or near-zero emission alternatives. From just one such dual-fuel ship in 2018, there are now nineteen. By the end of 2025, CLIA projects that 23 ships with fuel-flexible engines (including the first tri-fuel vessel) will be in operation; by 2036, up to 32 dual-fuel ships are forecast, some capable of using LNG, others methanol.
The report also shows a significant rise in ships that can use onshore power supply (OPS) in port, enabling shut-down of engines while docked. In 2018, fifty-five ships (representing about a quarter of the fleet) had this capability; the number has since grown to 166 ships, covering 58 percent of the fleet and 65 percent of passenger capacity. Forecasts indicate that by 2036 more than 270 ships will have OPS capability, drawing on retrofit pathways and new builds.
Other environmental practices are increasingly widespread. Advanced wastewater treatment systems (AWTS) are now fitted aboard many ships, exceeding MARPOL Annex IV requirements in many cases. Freshwater production onboard has similarly become standard across the fleet, reducing reliance on external supply.
CLIA’s president and CEO observed that cruise lines are investing tens of billions of dollars in new ships—over 80 vessels currently on order worldwide—to incorporate environmental innovations such as dual-fuel engines, advanced wastewater systems, air lubrication systems, and OPS connectivity.