The biology of the South American sea otter (Lontra felina) is scarcely known along the Chilean coast. In this study, habitat use during day time, and the behavior of this species are described, and compared between two localities: a protected embayment inhabited by artisanal fishermen and, an area of difficult access, both on the central-southern coast of Chile. The study was carried out at the end of 2005 and beginning of 2006. Despite the vicinity of the two studied localities (separated by ca. 9 km), there were differences in the time of peak diurnal activities, in duration of diving, and in the proportion of time devoted to socialization. At the most isolated and exposed locality sea otters were seen more frequently transiting in the water, and making long dives, while at the protected site, in vicinity of the fishermen village, diving was more frequent and shorter. Habitat use was also different between localities according to the presence of human activities. Some of these results contrast with other reports from Chile and highlight the need to improve the knowledge of the factors affecting the behavior of Lontra felina.