zoanthid
A type of colonial cnidarian resembling sea anemones, often found in sandy areas. The Japanese name literally means 'sand purse'.
Zoanthids are relatives of sea anemones that live in sandy areas.
Katakana spelling is standard for this organism; usually written in kana.
Kanji spelling is rare; the word is usually written in kana. The kanji 砂巾着 literally means 'sand purse'.
From 砂 (すな, 'sand') + 巾着 (きんちゃく, 'drawstring pouch'), referring to the sand-encrusted, purse-like appearance of the colony.