The black clams used here are dug by hand from La Unión's mangrove flats at low tide, a harvest so tied to the tide chart that vendors' stock literally depends on the moon.
Black clams or mixed shellfish served raw or lightly cooked in a chilled tomato-lime cocktail sauce with onion and cilantro, spooned into plastic cups. La Unión's port-side stalls sell it as a refreshing hot-weather snack.