This cluster of white tubes was growing within a kelp holdfast. The entire patch was small, only ~1 cm across.
I'll zoom in a few more times, because when viewed up close these animals are quite intriguing.
The picture below highlights the elongate white tubes on the right and also provides your first glimpse of the animals themselves. On the left side, look for the rings of tentacles radiating out from the tube entrances.
Here's an even better view of those rings of tentacles, also known as lophophores:
This is a bryozoan called Tubulipora. When feeding, the colonial animals extend their lophophores into the water to capture food particles. But they can also retract their tentacles into their calcareous tubes (see diagram below). When they do so, sometimes you can just barely see the tips of the tentacles near the tube opening or aperture (see picture following diagram).
Modified from Invertebrates (Kozloff 1990)
Tubulipora belongs to the most ancient class of bryozoans known as the Stenolaemata. They're known for having thin, porous walls (see below), and many, including Tubulipora, lack operculums (trapdoor-like structures that close off the tube entrances). [For a picture of an operculum in another species, Eurystomella, click here.]
Although they just look like tiny white patches of lace growing on kelp when observed in the field, I hope this helps you visualize what these animals look like when they're out and feeding.