This week divers from different coastal communities around the world wrapped the bright yellow crime-scene tape around dead coral reefs in a series of underwater dives.

The divers, associated with the climate change advocacy group 350.org, went underwater marking dead coral reefs in Samoa, the Australian Great Barrier Reef, and the Andaman Islands to bring attention to the “worst mass coral bleaching in recorded history” and blamed the “reckless behavior of Exxon and fossil fuel companies” for the damage and for posing a hindrance to the work of climate change activists.

“The rapid death of so much coral worldwide this year is a tragedy for the people who depend on these ecosystems. It’s made more hideous by the fact that it could have been prevented, had Exxon and its ilk simply told the truth about climate change when they knew it,” 350.org’s senior advisor and co-founder Bill McKibben said in a statement. “It’s not hyperbole to say they killed the reef; it’s just physics and biology.”

The divers held signs underwater that read #ExxonKnew referring to the 2015 investigative report by non-profit climate change news organization Inside Climate News. The report found that Exxon’s own research decades ago revealed the ill effects of global warming and the company buried the information, creating doubt about the existence of climate change, which its own scientists confirmed.

The climate change advocacy group accused Exxon of “pouring resources to actively deceive the public by funding climate denial groups, recommending against climate shareholder resolutions, and obstructing climate action.”

“We need to remember that there’s nothing natural about this horror. It was caused, as so many crimes are, by greed. And that greed is ongoing – Exxon continues to search for more hydrocarbons, and to reject even modest changes to its policies,” McKibben wrote in the Guardian Wednesday.

“That’s why we’re wrapping crime scene tape this week around those bleached coral heads, those dead staghorns. That’s why we’re taking crime scene photos with underwater cameras. That’s why we’re protesting on the reefs. We’re not going to let them get away with murder.”