This study examined the influence of spending time outdoors on young children's physical and socioemotional development. We observed preschoolers' activities in two naturally provisioned outdoor environments over the course of one year. Eleven preschoolers were videotaped continuously for 16 days at a local river and 9 days at a creek adjacent to the school. In addition to the quantitative analyses of children's behaviors, a case study of three children's experiences over the course of the year was conducted. Both the river and the creek settings encouraged a multitude of physical and play behaviors with similar types of affordances, including flat surfaces for running, rocks for climbing and jumping off, and water for exploration and play, but the wilder environment (river) afforded more risk and personal challenges. Observations of children's motor activities, play and responses to challenging environmental features supported the importance of accumulated experience and social context for the development of confidence in the face of risk, individual exploration and positive social support and engagement with peers.