Oil traders once again believe it is worth heading crude oil out to sea. The market structure for Brent crude, the benchmark for more than half the world’s oil, now makes it viable to store supplies in a ship to potentially lock in profits on a sale six months later.

In August, cargoes for later delivery have averaged $2.78/bbl higher than prompt shipments, more than covering the cost to hire a tanker for storage for half a year.

This discount of near-term supplies versus cargoes for later, known as contango, was as little as 70 cents in April, when shipping costs were higher as well, making it unlikely then that traders could potentially profit from floating storage. But with front-month futures sliding since early June and tumbling into a bear market this month amid swelling onshore stockpiles, the market structure has changed while freight has also become cheaper.

A six-month time charter on a Very Large Crude Carrier that can carry about 2 MMbbl of oil would cost $25,000 to $28,000 a day, according to two shipbrokers and a tanker charterer. That is equivalent to $2.25 to $2.52/bbl. October Brent futures traded at $43.76/bbl, lower than the April 2017 contact at $46.23 on the London-based ICE Futures Europe exchange.

Most varieties of crude from Africa, North Sea and the Asia Pacific region are priced off the Dated Brent benchmark, meaning traders can potentially benefit from holding on to such grades at sea. Apart from freight, storing crude on tankers would also involve costs including that for ship fuel, insurance and finance.

A drop in freight rates as new ships enter the market and shrinking availability of traditional storage options “may be prompting creative approaches to holding on to oil,” industry consultant JBC Energy GmbH said in a report last month. Additionally, the deepening contango has made floating storage relatively attractive for some companies, it said.