Only a scattering of light penetrates the deep water, more than 300 feet beneath the ocean surface off the coast of Guam. It’s like twilight to the human eye, even in the middle of the day.This part of the ocean, known as the upper twilight zone, is one of the least explored ecosystems on Earth because it’s so difficult, expensive and dangerous to reach. It’s only accessible by submarine, remotely-operated vehicle or by specially trained technical divers.But humans are starting to unravel the mysteries of life here. In November, a group of scientific divers from the California Academy of Sciences successfully navigated a series of perilously deep dives.AdvertisementAdvertisementAdvertisementAdvertisementTheir mission was to fetch monitoring devices lodged in Guam’s deep reefs that have been collecting data on marine life and ocean temperatures for more than eight years.The divers found a swath of ocean populated by weird and wild creatures, from delicate corals and shimmering worms to spiky sea slugs and hairy crabs. The monitors are also providing an insight into temperature changes, suggesting climate change may be having an impact even in these deep waters.Divers ascend after installing monitoring devices in Guam in 2018. Only specially trained divers can reach the ocean’s upper twilight zone. – Luiz Rocha/California Academy of ScienceDiving to the ocean’s upper twilight zone is a treacherous endeavor. Standard gear simply doesn’t cut it at these depths — recreational divers breathing compressed air don’t venture below 130 feet. Instead, trained technical divers need specialized equipment allowing them to breathe a cocktail of helium and air.The deeper the divers go, the more gas gets dissolved into their bodies, and it needs to come out very slowly to avoid decompression sickness, known as the bends, where bubbles form in the blood causing severe pain and even de …
