This is a horse conch... let the jokes commence...
The Florida horse conch (Triplofusus giganteus) is one of the largest univalve gastropods in the entire world. Its shell can get up to 24 inches (60 cm) long and is found on the Atlantic coast of North America, ranging from North Carolina down to the Gulf of Mexico. They feed on other gastropods and can even be cannibalistic. Despite the shape of the shell (and the common name), this isn’t a true conch because it isn’t in the Strombidae family.