A Christmas repost from a few years ago. Spirobranchus giganteus are beautiful underwater creatures, only about 1.5 inches tall, which look like tiny decorated Christmas trees. They are almost too attractive to be described as what they are, tube-building polychaete worms. They are, however, often referred to as Christmas tree worms. Each worm has two brightly colored crowns that protrude from its tube-like body. The crowns look like miniature fir trees often in a wide range of brilliant colors. The worms live in tropical waters around the world. Here is a video of spirobranchus giganteus, Christmas tree worms, from Taiwan.

Spirobranchus giganteus in Green Island, TAIWAN