The world's oceans cover two-thirds of our planet but we've only explored about 10 per cent of its depths. Alvin can only do so much, so the US Oceanic and Atmospheric Administration (NOAA) has relied on a twin pair of Deep Sea Vehicles (DSV) to explore the waters around Hawaii for over a decade and what they've found has already changed history.
The Pisces IV (and its twin sister, Pisces V) is a battery-powered DSV capable of shuttling a crew of three as deep as 2000 metres — not nearly as deep as China's Jialong class DSV, but sufficient for the water around Hawaii in which they primarily operate. The Pisces were originally built by Hyco International Hydrodynamics in Vancouver for use by the Department of Fisheries and Oceans of Canada where it completed over 1880 dives throughout the Atlantic, Arctic and Pacific oceans before budget cuts forced the cancellation of the Pisces program in 2000. The ROPOS ROV now performs their duties in Canada, while the Pisces IV and V have been adopted and modernized by the Hawaii Undersea Research Laboratory arm of the NOAA.
The Pisces IV is six metres long, three metres tall and displaces 14 tonnes. Its bathysphere is roomy enough to accommodate three people and its life-support systems allow for 7-10 hour dives, though its emergency back-up system can keep them alive for up to five days. A pair of lead-acid batteries power a pair of side-mounted thrusters, which can propel the DSV at speeds up to two knots.
While they are capable of collecting samples and placing probes with a pair dexterous manipulator arms, a majority of the data they collect is from a pair of front-mounted video cameras. They utilise a low-light black-white camera for filming shy underwater creatures that would be startled by the subs' bright spotlights in natural lighting conditions at depths of 30 metres as well as anInsite Pacific MINI-ZEUS HDTV camera camera. The on-board scientists can also see the sea for themselves through a trio of forward-facing 6-inch acrylic view ports.
Both DSVs are transported to dive sites around the 50th state aboard the R/V Ka‘imikai-o-Kanaloa. They are only launched during daylight hours as they are serviced every evening. Typically one DSV is launched at a time with the other held in reserve in case of an emergency (they can become entangled in discarded fishing lines, for example, and need the other to help extricate them) though they can be launched simultaneously if the research requires it. They often dive near the undersea volcano Lo‘ihi and submerged banks of the Big Island as well as the sea mounts to the Northwest. Every year, researchers discover new species of deep sea life with the help of these DSVs and in 2002, they even stumbled upon the midget sub that Japan stationed in Pearl Harbor just before their attack. That 24m midget was scuttled by the USS Ward in our opening salvos and remained lost at the bottom of the ocean for 61 years. This was only the third time that the Pisces had dived together but the discovery, according to HURL's associate director, John Wiltshire, was "probably the most significant archaeological find in the Pacific". [Wikipedia - NOAA - SOEST 1, 2]