White Seaweed

I was walking the other day over an exposed basalt flow at the coast when I came upon tide pools (or rain pools) on the top of the expanse of rock.

In the top picture shows the pool.  There's a large expanse of the growth at the lower-leftish corner of the pool and a much smaller, linear growth near the pool's middle.

I didn't think to wonder what kind of water was in the pool--it was on top of the rock, well above the barnacle line, so I'm not sure how often the waves would be able to replenish it.

In the clear water was translucent white grass or hair or maybe seaweed.   It reminded me of tapeworms, so I didn't want to touch it.

The camera does a good job with the macro lens, so I was able to get some close-ups of what the stuff looked like.  It seemed to be a plant which was taking advantage of a small seam in the pool.