Deep in the warm, sunny sea lies a busy city built by tiny animals. It is called a coral reef. Each lump of coral is made by thousands of soft little creatures called polyps, and every polyp is no bigger than a grain of rice. 🐠 Very slowly, over hundreds of years, the polyps build hard, colorful stone homes that grow into a giant reef. A reef bursts with life: striped clownfish dart between waving sea anemones, green turtles 🐢 glide past, and hungry sharks patrol the deep edges. Coral needs clean, warm water and plenty of sunlight to stay healthy. But when the sea grows too hot, the coral turns ghostly white — this is called bleaching, and it can make the coral very sick. That is why people all around the world work hard to keep the water clean and protect these amazing underwater cities. 🪸