The purple creature with long branches is a soft coral called sea fan (Menella michaelseni ).  Its branches are long and look like whips. Even the weakest current will make it move around. Its surface is covered in slime. If you touch it with a cloth, it will turn into a reddish purple color. The spicules are also dark reddish purple.

Polyps that look like small sea anemone can be found all over its branches. When it stretches its tentacles, the polyps are 3 mm in diameter, catching planktons and organic matters flowing in the current. They are often spotted in lava slopes 20 m to 40 m deep around Sakurajima.