Energy traders and power utilities are storing more liquefied natural gas at sea, an unusual move to hoard supply for winter as the market faces a severe shortage.

Energy-starved utilities in Europe are parking LNG shipments off the coast in a scramble to replace Russian pipeline gas this winter. They can’t simply import the fuel into onshore storage because terminals are maxed out, and so are choosing to pay to keep the ship nearby.

Importers in Asia and South America have also jumped on the floating storage bandwagon, seeking extra supplies. At the same time, traders are looking to profit by storing LNG and cashing in when prices spike during the winter months.

LNG volumes in so-called floating storage globally hit 1.4 million tons on Sept. 2, the most in two years, according to energy intelligence firm Kpler. That’s nearly equal to Spain’s total imports in August.

The strategy, used frequently in the oil market, is rare for LNG because the liquid fuel slowly evaporates in the ships, making long periods of storage challenging. That illustrates the lengths that gas importers will go to in order to ensure they have enough fuel this winter.

There are at least nine vessels storing LNG in the ocean, according to Bloomberg and Kpler shipping data. The tanker British Partner was idling in the South China Sea this month after loading a cobbled-together cargo of Omani and Qatari gas via ship-to-ship transfer near Malaysia, Bloomberg data show. Meanwhile, the Aristidis I is waiting in the Caribbean with Dominican Republic-origin and US gas onboard, said Mathew Ang, an analyst at Kpler.

Natural gas prices in Europe and Asia are trading at a record high for this time of year as Russia curbs supply to key customers, intensifying competition for LNG shipments from suppliers like the US, Nigeria and Qatar.

The demand for ships globally is driving freight rates higher, and traders say they still have room to climb. In a sign of how short the market is, energy majors are refusing to release their vessels as they typically do at the end of summer.

“We would expect there to be more floating storage,” said Oystein Kalleklev, chief executive officer of shipowner Flex LNG Management AS. “However, the LNG gas carrier market is mostly sold out for the winter, so we would expect traders to utilize the ships in their existing portfolio.