 In the late 1950s, the discharge of methane gas in the depths of the river caused the water to bubble, and the toxins wore away at boats' propellers.The decline of heavy industry and tanneries, reduced use of oil-pollutants and improved sewage treatment have led to much better water quality compared to the late 19th and early- to mid-20th centuries and aquatic life has returned to its formerly 'dead' stretches.Alongside the entire river runs the Thames Path, a National Route for walkers and cyclists.