The group of inventions relates to the field of organic chemistry and can be used for collecting films of petroleum, oils, mazut, fuels, hydrocarbons and other petroleum products with the aim of cleaning the surface of water, and also for cleaning water flows which have been contaminated by petroleum or petroleum products. A substance for collecting petroleum or petroleum products from the surface of water includes a natural polymer and additionally includes a biodegradable surfactant in the form of an aqueous solution with a concentration of no less than 0.1 g/L, and, as the natural polymer, contains polysaccharide microgels having a mass of between 20,000 and 200,000 daltons and a particle size of between 50 and 600 nm in the form of an aqueous solution with a concentration of no less than 0.2 g/L, wherein the ratio of polysaccharide microgels to biodegradable surfactant is between 12:1 and 2:1. Methods for collecting petroleum or petroleum products from the surface of water include processing the surface of a film of petroleum or petroleum products using a reagent, and then collecting the product of the reaction thereof. The reagent consists in polysaccharide microgels having a mass of between 20,000 and 200,000 daltons and a particle size of between 50 and 600 nm. According to a first variant, before or after spraying the reagent, a biodegradable surfactant is used for processing a film of petroleum or petroleum products, or a portion of said film; or, according to a second variant, the reagent is first mixed with the biodegradable surfactant until achieving a ratio of polysaccharide microgels to biodegradable surfactant of between 12:1 and 2:1. The technical result consists in decreasing the specific consumption of reagents used in the process of collecting petroleum or petroleum products from the surface of water, in enhancing the surfactant qualities of reagents, and also in reducing the residual amounts of said reagents in water.