Some scientists now worry the beauty of Australia's Great Barrier reef may never recover.
The reef is a diverse wonderland of colourful coral and abundant ecosystem of fish and sea animals.
But in March, the reef suffered its third coral bleaching event in the last five years.
Coral reef researcher Terry Hughes says - that's a red flag for the reef's future.
"We're very concerned as scientists about the shrinking gap between one bleaching event and the next. They are no longer rare events, they're happening more and more frequently."
February 2020 was the hottest month the reef has experienced since records began in 1900.
How bleaching works is warm waters cause the coral to expel living algae then, the coral calcifies and "bleaches", turning white.
Hughes added that he is now almost certain that the Reef won't bounce back to what it looked like five years ago or even 30 years ago.
And while you may have seen video online of nature moving back in while the world is locked down, Hughes says that's had little impact on the Reef's decline.
"The Great Barrier Reef is doing it's own thing regardless of how many tourists are snorkelling around on it. Tourism has very minimal impact on the Reef itself and as we saw in March the presence or absence of tourism doesn't make any difference in terms of global warming. So, you know, we're at a fork in the road if business as usual will eventually destroy the Great Barrier Reef as we know it.
The reef spans a vast area, nearly 1400 miles long.
It was world heritage listed in 1981 as the most extensive and spectacular coral reef ecosystem on the world.