Slow steaming is not only a way for shipowners to save on their fuel bills, it can help save whales.
When California enforced rules limiting vessels transiting its ports to using bunkers containing just 0.1% sulphur, researchers found the higher cost of the fuel caused shipowners to reduce speeds.
In one shipping lane along the state's coast, the US National Oceanic and Atmospheric Administration (NOAA) saw speeds drop from about 20 knots per hour in 2008 to just over 13 knots per hour in 2015.
