This Lottia scutum (Plate Limpet) has seaweed growing from its shell.
Here's the beautiful Osmundea spectabilis (Sea laurel, red sea fern).
This seaweed is Odonthalia floccosa (Sea Brush), and it's abundant these days at North Beach.
This Egregia menziesii (Feather Boa Kelp) is one of the most common seaweeds this time of year at North Beach.
This Mazzaella splendens (Iridescent Seaweed) is beautiful when it's under water and the sun shines on it.
Another very common seaweed at North Beach: Fucus gardneri (Rockweed).
This is Smithora naiadum (Red Fringe), growing on eelgrass.
Here's an Ulva spp. (Sea Lettuce), which is very common at North Beach.
The Alaria marginata (Broad-winged Kelp) looks prettiest when sand fills its grooves.
You can find fresh Nereocystis luetkeana (Bull Kelp) on the beach these days, or examples like these, slightly dried out already.
Not the greatest shot, but it's a pretty slug. Many thanks to Jeff for pointing this out (again).