Is it true that over 95 percent of a jellyfish is water?

Yes, it is true. A jellyfish is plankton with no heart, bones, blood, or gills; over 98 percent of it is water, so it looks transparent like a clear umbrella. Its body has two germ layers with a thick jelly layer between, and a simple body cavity lined with stomach skin with a single opening for both eating and excreting.