Rainwater killifish can be found from Cape Cod, Massachusetts southward through the Atlantic, and in areas near the Gulf of Mexico. These fish can tolerate a wide range of salinities and are found in marshes, bays, lagoons, and springs. They tend to primarily inhabit brackish water in calm, vegetated area. Rainwater killifish usually swim several inches below the surface of the water and are commonly found in the St. John’s River system and in Florida’s springs. They feed on larval crustaceans, mosquito larvae, small worms, and mollusks.