Not the kind you make from fruit, but the gelatinous, often translucent, floating animals you rarely see in the water. The Monterey Bay aquarium houses an amazing collection of such jellies, many of them common along the California coast.
Sea jellies, often mis-named jellyfish (although they are not at all closely related to fish), are very simple animals consisting basically of water and gelatinous goo.
A circular nerve net coordinates the contraction of muscle cells at the edge of the umbrella, giving them the ability to move slowly through the water. Tentacles lined with stinging cells stun prey that come into contact with them, and ciliated cells in the tentacles then slowly move that food toward the central opening in the underside of the bell, where it enters a gastric cavity for digestion. There are really no organ systems per se, but simply cells specialized for specific tasks.
Even though these sea jellies would seem to offer so little nutrition to other consumers, they are favorite prey items of sea turtles and some sea birds. Unfortunately, the many plastic bags floating around In our oceans also look like sea jellies, and vertebrates that eat those instead often end up starving to death from digestive tracts impacted with plastic.