WW: Vertical tidepool

(This chunk of 30-inch concrete culvert was probably rolled off a construction barge and into the bay as surplus at some point in the past. In the meantime it's been colonised by a wealth of sea life, including most conspicuously at least two species of starfish. The community is located well below mean low tide, and only fully exposed at minus 4. I'll bet it's a great visit at high tide, with…