Constructed as a research vehicle to operate at depths of up to 11,000 metres (36,000 ft), it was designed to explore Challenger Deep, the deepest surveyed point in the global ocean.

Nereus had a lightweight robotic manipulator arm to conduct the sample collecting that operates hydraulically and was able to perform under intense pressure.

[4] As an alternative to the tether, the Nereus could be switched to a free-swimming mode and operated as an autonomous vehicle to survey the ocean floor.

[3] In designing the vehicle, the design team led by Andy Bowen at the Woods Hole Oceanographic Institution relied on previous experience in developing autonomous underwater vehicles (AUVs) and tethered robots to build a hybrid ROV that could both fly like an aircraft to explore large areas of the ocean floor, but would be easily converted to able to hover over the small areas to conduct experiments or collect samples of rocks and sea life.

[5] The May 2009 dive by the Nereus achieved a depth of 10,902 metres (35,768 ft), making it the world's deepest-diving vehicle then in operation, and the first since 1998 to explore the Mariana Trench.

The first was the crewed Bathyscaphe Trieste, which carried U.S. Navy Lieutenant Don Walsh and Swiss engineer Jacques Piccard and made the voyage on 23 January 1960.

"[7] On 10 May 2014, at around 2 p.m. local time, Nereus was lost while conducting a dive at 9,900 metres (32,500 ft) in depth in the Kermadec Trench, believed to be caused by extreme pressure at up to 110 megapascals (16,000 psi).