Total yeast counts at 20 and 37 C incubation from chlorinated salt water pools containing marine mammals averaged 40 per L and 12 per L, respectively. Candida albicans, the etiological agent of candidiasis in mammals, was found in 32% of 123 water samples although numbers were low (average of 1.2 cells per L). Theyeast was isolated only once from feces from one Atlantic bottlenosed dolphin (Tursiops truncatus) but was recovered from three fecal samples from an asymptomatic beluga whale (Delphinapteras leucas) which suggested that this animal may be a carrier. Three yeasts (Candida tropicalis, C. parapsilosis, and Torulopsis glabrata) associated with human disease accounted for 73% and 88%, respectively, of the 37 C isolates from water and animals. The data indicate the routine presence of potentially pathogenic yeasts in water and various marine mammals. Captive environments characterized by antimicrobial treatment (e.g., chlorine) may provide appropriate conditions for resistant microorganisms, including yeasts, to become opportunistic pathogens in susceptible marine mammals or to become established in others which act as healthy carriers.