Coral bleaching in Okinawa, Japan, captured by the XL Catlin Seaview Survey in September 2016. (XL Catlin Seaview Survey)

The underwater world that snorkelers and are known for the vibrant, rainbow colors of coral. But coral bleaching, a whitening of the coral due to a loss of the algae living within the tissue, is transforming some of the world's most important natural wonders and threatening some of the most colorful, richest marine habitats on Earth.

Coral bleaching is caused by increased sea temperatures or extreme weather conditions.In 2005, the in one year due to a massive bleaching event caused warmer water temperatures, according to NOAA. And more recently,extensive aerial surveys and dives revealed that by coral bleaching, due to record-warm water driven by El Niño and climate change that has cooked the life out of corals, Climate Central reported.

A unique global study, the is working with some of the world's leading scientific institutions to monitor coral bleaching. The surveyis creating a baseline record of the world’s coral reefs, in high-resolution 360-degree panoramic vision, helping monitor changes in coral reefs over time. The stunning images the XL Catlin Seaview Survey are capturing are also helping the public see and understand the issues reefs face.

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As the worst global bleaching event extends to its third year, the survey embarked on an expedition to Okinawa, Japan in September. It has captured some of the most devastating images of coral bleaching— a mixture of bleached, fluorescing (which produces a bright, spectacular color but occurs when corals are stressed)and dead corals around the Japanese islands.

Stephanie Roach, the underwater photographer from the XL Catlin Seaview Survey expedition to Okinawa, told The Guardian the bleaching was widespread in the shallow areas, generally under about six feet in depth. In that region almost all the branching coral, called acropora, was bleached, if not dead. "The fluorescing was spectacular, especially the corals that were glowing a brilliant shade of blue," she said.

The XL Catlin Seaview Survey alsoreleased spectacular bleaching imagery from New Caledonia earlier this year. View the slideshow above too see photos capturing coral bleaching in both Okinawa and New Caledonia. For more on XL Catlin Seaview Survey and coral bleaching, visit .