They were "not even sure if they were there," he said.
The reef he was used to was the most beautiful in Hawaii, he told CNN. "It was an incredible coral garden with thousands of colorful fish."
But now everything was gone. "It looked like a parking lot," Kosaki said. "There were hardly any debris left."
Climate change causes more frequent hurricanes
Kosaki is the deputy head of the National Oceanic and Atmospheric Administration for the monument.
Most islands in the archipelago, which extend west of the main islands of Hawaii, are uninhabited. This was the first time that researchers had the opportunity to look deep below the surface. [1
Corals are resilient, but the situation is becoming increasingly difficult due to the "onslaught of climate change".
Heavy hurricanes like Walaka occur now more often. Since reefs may take several decades to recover after a major weather event, reefs like Rapture might be hit by another storm or coral bleaching before they had a chance to fully recover after the last trauma.
In the reefs used to live thousands of multicolored fish species. "When the coral disappears everything disappears."
Monitoring the resurgence of these reefs "will be a project that leads me through my retirement," he said.
The name for the Marine National Monument combines two Divine figures in the Hawaiian tradition, Papahānaumoku and Wākea – essentially Mother Earth and Father Sky.
This tradition teaches that all life was originally born of coral polyps, Kosaki said – not very different from what evolution teaches.
"Cultural resources and natural resources are one and the same for Hawaiians," he said.