Psychedelic Elvis Worm: Filming Life at the Ocean's Last Frontier

Eleanor Mortimer's new eco-documentary How Deep Is Your Love accompanies a scientific expedition to the deep Pacific, a realm where roughly 90% of life has yet to be named and new species surface on a daily basis.

For the marine biologists on board, the answer to the film's title question sits about 5,000 metres down. In the ship's lab, the camera watches them observing, describing and classifying the strange creatures that survive in the freezing waters of the abyss: blobby little sea pigs and alien, glow-in-the-dark sea cucumbers.

"It is the last frontier of exploration on Earth," Mortimer explains in a voiceover she delivers with deadpan, quirky charm. Her film frames the deep sea as a place of abundance — and of mounting threat from sea mining.

The expedition targets the eastern Pacific. The ship's robot takes four hours to descend the four kilometres to the ocean floor, where it trundles across the sediment with its grabber claw at the ready. One biologist states that 80% of what the team brings to the surface is new to science.

The film captures the wonderstruck awe on the scientists' faces as they clap eyes on never-before-seen creatures. That reaction becomes one of the documentary's central pleasures.

Formal recognition moves slowly. Acquiring a Latin name for a new species can take years, so in the meantime scientists assign informal monikers — including the Headless Chicken Monster and the Psychedelic Elvis Worm, a creature that gives the film some of its most memorable imagery.

The documentary's timing carries weight. With deep-sea mining advancing as an industry, the creatures Mortimer films — most of them still unknown to science — face the prospect of disruption before anyone has even named them. The film opens the Guardian's coverage on 30 September.