The lookdown (Selene vomer) is a marine fish recognizable by its laterally compressed body, almost triangular shape, and silvery sheen. It lives in the coastal waters of the western Atlantic, from the Gulf of Mexico to the Caribbean, where it frequents sandy bottoms and estuaries.

The lookdown has a metallic appearance with a brilliant bluish sheen. Its tail is a translucent, bright yellow.

Its strongly laterally compressed body has an almost triangular shape, accentuated by a prominent forehead. Its mouth is located on the lower part of the head. The lookdown has dorsal and anal fins whose front rays are particularly elongated.

The lookdown typically averages around 14 inches in length, but the largest individuals can reach nearly 20 inches.

The lookdown is widely distributed throughout the western Atlantic, along the U.S. coast from Maine south to Florida, and along the coast of Central and South America as far south as Uruguay.

The lookdown is also found in the Gulf of Mexico and around the major Caribbean islands, including Cuba, Jamaica, Hispaniola, Puerto Rico, the Bahamas, and the Lesser Antilles, extending south to Trinidad and Tobago.

The lookdown undertakes extensive seasonal and annual migrations to reach spawning grounds or areas more suitable for overwintering.

The lookdown frequents brackish waters and moves in schools, whose numbers help protect it from predators. In addition, the metallic flashes of light coming from all directions make it harder for predators to spot and isolate an individual fish.

The lookdown feeds mainly on small crustaceans, such as crabs and shrimp, as well as worms and small fish, which it hunts primarily at dawn and dusk.

Juveniles develop near estuary mouths, where mangroves provide shelter and food.

Juveniles differ from the shiny, silvery adults by their broad, dark, slightly oblique vertical bands and a dark band running across their eyes. The first rays of the dorsal and anal fins are also greatly elongated, forming long filaments that shorten as the fish grows.

The lookdown is listed as many other marine species within The IUCN Red List of threatened species. The lookdown appears in the IUCN Red List since 2015 within the category Least Concern !