Soak the seaweed in warm water for 20 minutes to allow it to expand. Rinse well in a couple of changes of water, then drain and squeeze dry.
Heat the oil in a pot over high heat and sauté the garlic and mussels or clams for 1 minute. Add the seaweed and sauté for 1 more minute. Pour in the water and bring the mixture to a boil. Reduce the heat to low and simmer