During periods throughout the summer months there may be a large amount of Sargassum, a brown seaweed, that washes up on the shore which aids in shore development by acting to hold sand in place, which can eventually build up the shoreline.
He may have been referring to Sargasso seaweed from coral reefs, which can been seen washed up on shore after a major storm off of the NC coast.
It spends its life among sargasso weed (Sargassum spp.) floating in tropical seas where it is well camouflaged.
Sargassum muticum has a range stretching from Campbell river, British Columbia to Baja in California.
Sargassum muticum, also known as the Japanese wireweed, is a large brown seaweed of the genus Sargassum.