The bubble coral has large fleshy polys that inflate during the day for photosynthesis, and deflate at night to put tentacles out to feed. Often mistaken as plants, corals are in fact animals with plant-like cells living in their tissues. Corals build the largest living structures on Earth, and these reefs are so big, they are visible from outer space. With their tiny, tentacle-like arms, they capture planktons and even small fish for food. Coral reefs are vital to the health of the ocean and support 25% of ocean life, acting like an underwater forest by providing habitat for a huge, biodiverse community of ocean life. Today, climate change is the biggest threat to corals, with warming waters causing mass coral bleaching and eventual death of these extremely slow-growing animals. In the last 50 years, over half of our coral reefs have disappeared.