Algae, olive green in colour, ends of blades very swollen, mixed with red alagae and tarspot algae.
This type of seaweed was attached to the rocks nestled by barnacles on many of the larger rocks in the tideflat areas. It has a pod-like structure and a bumpy texture.
For more information on the habitat, vegetation, and weather of the area where I made this observation, please see the journal entry for April 28, 2012 here on iNaturalist. This was one of the various seaweed species on the rocky beach that I knew I could identify fairly easily. The large air pockets on the ends of the plant made it easy to identify. Oddly, the species I wanted was Fucus gardneri, but iNaturalist has decided that doesn't exist, so I have to go with Fucus distichus. This seaweed was not common along the beach and I only saw a few patches like this one here and there. It grows in small clumps and, in the clump I saw, each part of the seaweed I saw was about 3 inches long.
Rockweed is a seaweed that grows in tidal saltwater habitats. The plant must be able to root itself into the sand and therefore seem to be clustered around larger rocks which may serve as a type of anchor for the plant. The tips of the plant are bulbs filled with water. Is the purpose of this to store water? Isn't the tide predictable enough for these creatures to survive with water?