This article provides a report of the behavior of a solitary sociable dolphin studied on the southeast coast of England in 2007. This is the first study of its kind in which behavior of such a nonhuman animal was systematically studied. By the time of this study, this young female was highly interactive with people in the water. People accompanied the dolphin for 18.4% of the 100 hr of observation, and their presence changed her behavior. The study recorded 39 different behaviors; feeding and resting behaviors declined in frequency in the presence of people. In addition, the dolphin exhibited behavior possibly hazardous to people in the water, which included preventing swimmers from leaving the water. The dolphin received several wounds, at least one of which was life-threatening. This article discusses the welfare implications for such animals.