Slithering sea creatures are a type of aquatic animal that move by undulating their bodies in a wave-like motion. Eels are a common example of this type of creature, and they can be found in both saltwater and freshwater habitats. They have long, slender bodies and can range in size from a few inches to several feet in length. Eels are carnivorous predators and feed on a variety of small fish and invertebrates.