The name “jellyfish” is often applied to a wide range of sea dwelling animals with soft bodies in the subphylum Medusozoa. Specifically, the “medusa” phase of the animal’s life cycle is what is commonly identified as a jellyfish. In this phase, the animal usually has an umbrella shaped main body (called a “bell”) with tentacles trailing beneath that contain stinging cells used for capturing prey.
Since they comprise such a large and wide-ranging group of marine creatures, jellyfish may come in many different sizes, shapes and colors, though they are often at least partially translucent (meaning their bodies are somewhat see-through). The smallest jellyfish can be about one millimeter long, while the largest species may have a bell measuring over six feet across, with tentacles trailing over one hundred feet behind them.