Yes. Diamondback water snakes (Nerodia rhombifer), also called diamond-backed watersnakes, live in Louisiana as part of their broader central United States range along the Mississippi River valley. Their documented U.S. range includes Louisiana along with Texas, Oklahoma, Arkansas, Missouri, Illinois, Indiana, Tennessee, Mississippi, Alabama, Georgia, Kansas, and Iowa, plus parts of northern Mexico.
They are nonvenomous watersnakes typically found in and around freshwater habitats such as lakes, ponds, marshes, swamps, streams, and rivers.
Source: Nerodia rhombifer (diamondback water snake) — Wikipedia