Accidents caused by cnidaria are common in Brazil, a country with an extensive coastline that is the site of intense leisure activity (HADDAD JR., 2000). Although there have been few papers published on this problem, some patterns have been observed for this type of sting, and the majority of cases reported in the Southeast and South regions of Brazil have been caused by Hydromedusae Olindias sambaquiensis , giving rise to injuries of moderate severity in the victims (HADDAD JR., 2000; HADDAD JR. et al., 2002, 2010). Other accidents observed have been associated, in smaller number, with the Portuguese Man o’ War ( Physalia physalis ), two box jellyfish (Tamoya haplonema and Chiropsalmus quadrumanus ) (HADDAD JR., 2000; HADDAD JR. et al., 2010) with systemic damage, and Scyphomedusae Linuche unguiculata with the condition known as seabather´s eruption (HADDAD JR., et al. 2001). Recently, careful observation of the skin marks left after contact with cnidarians has been valued as a key element in the identification of the species, which may make recognition of the agents associated with seasonal outbreaks possible (HADDAD JR. et al., 2010), thus helping to determine the first aid measures to be taken both for simple cases, such as using treatment with cold seawater and vinegar baths, and for more systemic problems, such as the hospitalization of the victims (HADDAD JR., 2000; HADDAD JR. et al., 2002, 2010). This communication reports an outbreak of activity involving Olindias sambaquiensis , with a photographic record of the specimens found on the beaches, linking them to the skin marks found on bathers. It discusses the clinical aspects, and comments on possible contributory factors to the genesis of this outbreak. The outbreak took place at five beach resorts in the far south of the State of Santa Catarina, namely Rincao in the municipality of Icara, Arroio do Silva in the municipality of Arroio do Silva, Morro dos Conventos in Ararangua, Gaivota in Balneario Gaivota and Bella Torres in Passo de Torres. The data for this study were obtained from the Icara Fire Department in the State of Santa Catarina, on the south coast of Brazil, and the images of bathers’ lesions and of organisms stranded on the beach were obtained from the local media (www.engeplus.com.br), during the period January and February 2010. The correlation between cutaneous lesions and the identification of the cnidarians responsible for the cases of poisoning was carried out by analysis of the images obtained, and compared with the standards presented by HADDAD JR. et al. (2010). Additional information on the first aid offered to the victims was supplied by the Icara Fire Department, and from the results obtained after treatment. In an attempt to explain the occurrence of the outbreak during the period in question, oceanographic data on the temperature of the coastal water were obtained from the Physical Oceanography DAAC website (http://poet.jpl.nasa.gov), the Modis sensor and Aquac satellite being selected. The meteorological data were obtained from the website of the National Meteorology Institute (INMET - www.inmet.gov.br) at the Santa Marta Grande Lighthouse station (SC). Satellite data on temperature were analyzed, taking the average for the last seven years (2003 to 2009) and compared with data for 2010, referring to January and February. The same treatment was applied to the air temperature data for 2009 and 2010, obtained from the Santa Marta meteorological station. For average wind speed and direction, hourly vectors were broken down into Cartesian coordinates for estimating prevailing winds, with daily and monthly data. According to the Icara Fire Department (SC), from 1st January to 20th February 2010, 3,368 cases of jellyfish stings were reported among bathers at the five beach resorts in the far south of Santa