25 bizarre creatures from the bottom of the ocean that look like aliens

The carnivorous "death-ball' sponge.

ROV SuBastian/Schmidt Ocean Institute Sea creatures have adapted to help them thrive in extreme environments.

Unusual features allow them to live thousands of feet below the surface.

Underwater robots give researchers a glimpse at some of these elusive, fascinating animals.

Ghosts, goblins, spiders, and wolves don't just show up in fairytales.

Some deep-sea creatures are named after frightening or mythical creatures thanks to their eerie appearances.

However, strange snouts, enormous eyes, and sharp teeth all help these animals survive the cold, dark depths of the ocean.

So much is unknown about the deep sea, and these unusual adaptations can teach scientists more about what life is like thousands of meters beneath the waves.

Scientists often need remotely operated vehicles to capture images and video of deep-sea species.

Watching them in their natural habitat offers insight into the behavior of fish, cephalopods, and crustaceans that don't often surface.

Some of these creatures could even contribute to medical breakthroughs.

For example, toxins produced by ribbon worms have been studied for their potential use in treating conditions such as Alzheimer's disease and schizophrenia.

Here are 25 bizarre ocean dwellers that show how mysterious much of our own planet still is.

Known as a living fossil, the frilled shark has retained features of its ancient ancestors.