In recent years water has been recognized as an important vehicle for extraintestinal infection. A variety of pathogens are acquired through occupational, recreational, and even therapeutic contact with water. The nature of nonenteric waterborne disease is often determined by the ecology of aquatic pathogens. Such infections are of basically two types: superficial, involving damaged or previously intact mucosae and skin; and systemic, often serious infections that may occur in the setting of depressed immunity. A broad spectrum of aquatic organisms, including viruses, bacteria, fungi, algae, and parasites, may invade the host through such extraintestinal routes as the conjunctivae, respiratory mucosae, skin, and genitalia.