San Quintin Bay is considered to be an area of high productivity because of its coastal lagoon characteristics. A research project was design to study: a) Zooplanktonic organisms. b) The density or the taxonomic groups in the bay. c) The di versity and distribution of zooplankton, d) The possible relations of the groups with the nutrient concentration and the primary productivity.CIENCIAS MARINAS (Mex.)v. 8(1), 1982. The zooplanktonic organisms are ordered into 23 grow , on which the crustaceans predominate, the suborder has the highest number of individuals and the Siphonophora Order the lowest. In the West Arm or Falsa Bay, it was observed that there was a notable abundance of gastropods, mainly of the Nassariidae family.