Volunteer water quality monitors represent the intersection between citizen science and environmental stewardship. Understanding what motivates participation will enable project managers to improve recruitment and retention. This survey of 271 volunteers from eight water quality monitoring organizations in the U.S. found the strongest motivators to participate are helping the environment or community and contributing to scientific knowledge. No variation by gender was found, but younger volunteers have different motivations and preferences than older volunteers. Volunteers value the communication of tangible results more than recognition or reward.