Biofilm is defined as a cooperative community of microorganisms embedded in an extracellular polymeric substance (slime). Biofilm may consist of a variety of different microorganisms, including pathogenic bacteria. Biofilm is of particular importance to the recreational water community because once a biofilm is established, the bacteria become extremely tolerant to disinfection and the slime becomes challenging to remove from a surface. In addition to the health concerns associated with pathogenic bacteria in recreational water, the slime makes surfaces slippery and aesthetically displeasing. This presentation will explain what biofilm is, how it grows and what other industries are doing to control biofilm in their facilities.