When most people think of edible seaweeds, they probably think of Porphyra, commonly known as nori, which is the most commercially important.
Halosaccion, however, is also quite safe to eat, and can be made into tasty soups or tempuras.
The young plants are best for eating and can be harvested in spring or summer (Roos-Collins 1990).
Links to seaweed recipes:
Roos-Collins, M. 1990. The Flavors of Home. Heyday Books: Berkeley, CA