PEARL HARBOR — Deep-dive technology has revealed a world of firsts to scientists who visited the Papahanaumokuakea Marine National Monument last month.

Sailing on the National Oceanic and Atmospheric Administration ship Hi'ialakai, scientists from NOAA, the Hawaii Institute of Marine Biology and Bishop Museum dived at that coral reef at depths not explored there before, witnessed new marvels and collected the first specimen of a recently discovered species of butterflyfish.

"We're going to these sites that no human has laid eyes on prior to this," said Randall Kosaki, NOAA deputy superintendent for the monument and chief scientist aboard the cruise that ended Sunday.

The mission was to test deep-dive mixed-gas technology that allows dives 200 to 250 feet down. With conventional scuba gear, divers can reach about 80 feet (much deeper records have been set with special scuba gear) and submersibles dive to 700 feet, giving the world information about the two extremes, Kosaki said.

But the area between — the deep coral reef that is well below 300 feet — is poorly explored and documented, he said.

"We literally have better maps of the moon than we do of our deep coral reef habitat," Kosaki said. "So there's a couple lifetimes of exploration to be done on these reefs."

At the 200-foot depth, the expedition found 12 to 15 species of fish never seen before in the monument, probably because scientists couldn't get down there to observe, he said. Also, some deep-water algae beds are serving as nurseries for young fish, which is entirely new to the researchers, he said.

"The biodiversity of coral reefs are a lot greater than we had anticipated. So as we continue to explore these deeper waters, I would expect that we'll add significantly to the number of fishes known in the Hawaiian archipelago and the Northwestern Hawaiian Islands," Kosaki said. "It just underscores the need to protect some of this biodiversity and to document it for future generations."

The ship had six crews of divers who made about 111 dives throughout the 30-day trip, said Kelly Gleason, a maritime archaeologist and dive facilitator. The crews made about two dives a day and could only stay down for about 20 minutes. It took 45 minutes to decompress and rise to the surface.

The mission of the divers was to characterize the environment at the 200- to 250-foot level and look for any invasive algae, Gleason said, adding that none was found.

Some things they came across were unexpected. For example, researchers expected sloping terrain but found dramatic ledges in some locations.

"Every dive we conducted was an opportunity to see something new," Gleason said.

Brian Bowen, a research professor at the Hawaii Institute of Marine Biology, said he's been on five trips to the area and this one was particularly exciting because it represents a major new frontier of exploration of the deep reefs that make up three-quarters of the reefs throughout the world. Scientists discovered big parrotfish, ulua and jackfish at the 200-foot level and Bowen wondered if these fish could be used to replenish the shallow reefs.

This deep-dive technology should help open research in other areas such as the Caribbean, as well, Bowen said.

And information obtained at the monument could help reef restoration efforts in other parts of the Hawaiian Islands, he said.

One significant discovery, that of the algae nursery beds, might change the way people use the ocean, Bowen said.

"If you're dumping trash in 170 feet of water you might be dumping it on the nursery ground that keeps your fisheries going," Bowen said.