Marine Envenomation.  Venomous aquatic animals are hazardous to swimmers, surfers, divers, and fishermen. Exposures include mild stings, bites, abrasions, and lacerations. Severe envenomations can be life threatening. This article reviews common marine envenomations, exploring causative species, clinical presentation, and current treatment recommendations. Recommendations are included for cnidaria, sponges, bristle worms, crown-of-thorns starfish, sea urchins, venomous fish, stingrays, cone snails, stonefish, blue-ringed octopus, and sea snakes. Immediate and long-term treatment options and management of common sequelae are reviewed. Antivenom administration, treatment of anaphylaxis, and surgical indications are discussed.