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is a sea cucumber a plant or animal?

The sea cucumber is not a plant. It's a marine animal! They are echinoderms which means they are related to starfish. There are about 900 species of sea cucumbers.

The sea cucumber may look soft, but it's covered by a thick, tough skin. The top skin covers many, microscopic pieces of skeleton called spicules. The shape of spicules is different depending upon where they are on the sea cucumber's body. These pieces of skeleton can be shaped like rods, disks, or plates. Some skeleton pieces are called anchors because they are used by the sea cucumber to anchor it to the bottom.

They vary in size, shape, and color. All sea cucumbers are tubular, but they vary in length. The shortest ones are about one-half inch and the longest ones are 16 feet fully extended! There are some species living at great depths with bright colored rings, spots, and stripes.