Detritus might be one of the least exciting parts of the food web, but the amazing color, shape, and behavior of some detritus eaters, like this California sea cucumber, make up for that.
This relative of sea stars and sea urchins crawls along the bottom picking up detritus with its tentacles and stuffing it into what might loosely be called a mouth. You can see a sea cucumber feeding in its natural habitat in this very short video captured by Laura James off Alki Beach, West Seattle.
You can see some of Laura's other amazing videos at Beneath the Looking Glass.
The California sea cucumber (Parastichopus californicus) is one of the more commonly eaten sea cucumbers, and it is occasionally seen by beach walkers at extreme low tides. The sea cucumber you're more likely to see on the West Coast at low tide is the orange sea cucumber (Cucumaria miniata) which often wedges itself between rocks, and when the tide is in, it uses its tentacles to grab plankton out of the water.
Another unrelated fact about for the curious, a sea cucumber doesn't "breathe" through its mouth, it uses its other end for that.