Contaminating material is extracted from a body of water by providing a floating bed on which plants such as Cat Tails can be grown with their roots hanging into the body of water over an area where extraction of contaminating material from the body of water is required, growing the plants to take up the contaminating material from the body of water and harvesting the upstanding plant mass by moving the bed to a harvesting machine which cuts away the plant mass leaving at least part of the root mass to continue growing into a new season. The bed can be returned to a location for the next season.