Cup Coral

Non-photosynthetic cup corals colonise every square centimetre of the blue hole's interior surfaces, thriving in conditions that would kill light-dependent corals because they rely entirely on capturing suspended zooplankton from the water column. Their bright orange polyps extend fully in the darkness of the cavern, making them appear more vivid than most reef corals seen in daylight. Cup coral colonies grow extremely slowly — a single colony may be decades old — and they serve as habitat for nudibranchs, shrimp, and gobies that would be exposed on open reef.