World Jellyfish Day is celebrated annually on November 3rd to raise awareness about the ecological importance and unique biology of jellyfish in marine ecosystems. These ancient creatures, which have existed for over 500 million years, are crucial for the food web and serve as important indicators of ocean health, with massive blooms often signaling warming waters and pollution. The day promotes understanding of their role as both predators and prey and their resilience without having a brain or heart.