anthozoan

While most corals grow as colonies in tropical waters, the Devonshire cup coral (Caryophyllia smithii) is solitary and lives in temperate parts of the ocean. It grows with its cup-shaped skeleton attached to a rock or even a shipwreck. When the tentacles are expanded, these tiny corals look just like anemones, with each tapering, transparent tentacle ending in a small knob. Devonshire cup coral often occurs in a variety of corals from white or orange.

(Photo source)

Tube Anemone (Order: Ceriantharia) by mad-as-a-marine-biologist

Tube-dwelling anemones are not in fact ‘anemones’ but different subclass of anthozoans. They are solitary, living buried in soft sediments. Tube anemones construct their tubes out of a fibrous material that is secreted from mucus and threads of nematocyst-like organelles. 

(submission from mad-as-a-marine-biologist)

From National Geographic Photo Of The Day; May 22, 2012:

Deepwater Whip Coral, Japan Brian Skerry, National Geographic

What looks like a tangle of gnarled cables is in fact a forest of deepwater whip coral in Suruga Bay. Each strand is studded with feeding polyps that reach tiny tentacles into the currents to grab floating food.

See more pictures from the November 2010 feature story "3 Degrees of Japan’s Seas.“