The sea anemone
These are a group of predatory, marine animals of the order Actiniaria. They form polyps that can range from 4mm to 2 meters in size, and lack a hydra stage in their life cycle. Most have a column shaped body, with a foot called a basal disk that allows them to attach to a surface. If under stress, these organisms can detach themselves from a surface to find an environment with more favourable conditions.
Their gastrovascular cavity forms both their mouth and anus. They usually have ciliated mouth parts which allow them to direct food particulates towards their mouth cavities. Some species use the aid of toxins to help them capture prey. Surrounding the mouth cavity are many tentacles with cnidocytes. Cnydae that sting are known as nematocysts; these have vesicles filled with toxins. When triggered, a harpoon is launched into the target, injecting venom.
Some species have been known to causes severe injuries to humans and were potentially lethal.