Striking, stinging, and simple. #WorldJellyfishDay Jellyfish may have an ethereal, almost hypnotic way about them – but their existence is one of the simplest in the sea. 🪼 These animals have no bones, blood, hearts, or even brains. Made up of about 95% water, jellyfish are some of the most elementary animals on our planet – yet their role in marine ecosystems is essential. 🌎 Thought to act as a barometer of ocean health, scientists continue to learn more about how these simple creatures fit into the complex world beneath the waves.