I can't comment on the Great Barrier Reef but as a scuba instructor I have been diving in Thailand for 25 years and over that time I have seen a significant increase in Coral bleaching which is a stress response where corals expel the symbiotic algae, turning them white and leaving them vulnerable to starvation and disease. Primarily caused by rising ocean temperatures due to climate change. Coral bleaching in Thailand has reached critical levels, with 2024 seeing up to 80% of reefs affected by high ocean temperatures exceeding 33°C in the Andaman Sea and Gulf of Thailand https://news.mongabay.com/2026/01/coast-to-coast-coral-assessment-reveals-thailands-reefs-losing-complexity