In Seeds of Doom, Dr Who was menaced by giant, ambulatory vegetables called Krynoids. The monsters weren't always called that. The scriptwriters named them Crinoids initially, until someone pointed out that crinoids were alive and well and filtering suspended particles from the ocean in an entirely unmenacing way.
Crinoids (sea lilies, feather stars) are elegant relatives of starfish and sea urchins. Many species have long stalks that hold the animal above the sediment. They look like strange flowers. And, like flowers, they were thought to be fixed in place. But in the late 1980s, stalked crinoids were observed moving very slowly, using the tips of their arms to drag themselves along. (This locomotion is known as the finger-tip pull. It could be worse.)
More recently, Tom Baumiller and Charles Messing filmed the tropical Atlantic Neocrinus decorus moving at a heck of a pace across the sea floor using the (commando) elbow-crawl. You can read the article on line here and see the Quicktime video here.
Nature is wonderful.