sea anemone 
noun
A sedentary marine coelenterate with a columnar body which bears a ring of stinging tentacles around the mouth.
- Order Actiniaria, class Anthozoa.
- Scattered about were sea anemones, reddish lumps in the daylight, but, I was told, when they opened at night their massed tentacles would be almost scarlet.
- There were sea anemones, lots of colorful starfish, and even some sea urchins.