Deep-sea desalination pods: Cleaner, cheaper water

Posted: February 03, 2026

In the Gulf region, desalination has proven it can make water-scarce areas habitable. The Ras Al-Khair Power and Desalination Plant in Saudi Arabia is one of the largest hybrid desalination plants in the world (hybrid plants use two or more desalination technologies). It’s capable of serving 3.5 million people in Riyadh, the capital city.

The plant uses two of the most common methods of desalination: reverse osmosis and thermal distillation. Reverse osmosis uses semipermeable membranes that allow the water to pass through them, leaving the salt behind. There are different thermal distillation methods, but they all essentially rely on heating water, then collecting and condensing the steam into fresh water.

The process comes at a cost: desalination is notoriously energy intensive, often requiring over 1 kilowatt-hour per cubic meter of water treated. In 2023, desalination services in the Middle East used energy equivalent to almost half of all energy used by the region’s residential sector. The plants are also massive, taking up valuable coastal property, and can be harmful to nearby marine life, both through the intake of seawater and the disposal of brine. Plus, building a plant is a very expensive endeavor, with each new site requiring extensive customization.

As a result, while modern desalination technology has been around for decades, it has failed to revolutionize how water is collected and delivered in most parts of the world, including in the U.S.

Still, the need for fresh water around the world is enormous, including in small island communities and in coastal cities which often do not have the space for a traditional desalination plant. To help meet the world’s water needs, desalination must use much less energy and become less expensive. And that requires modular desalination plants that could be plunked into a new site, with minimal customization, and easily scaled up or down.

Deep-sea desalination: the power of natural pressure

One emerging approach is to install desalination plants on the seafloor—ideally 300 to 600 meters below the waves.

At great depths, there is enormous pressure. While the conditions are incredibly dangerous for a human being, they’re a boon for startup Flocean’s desalination pods.

Flocean’s pods contain standard reverse osmosis membranes that sit parallel to the sea floor and are in contact with the water above. Below the membrane, on the permeate side, a pump creates a vacuum, lowering the pressure underneath and creating a pressure gradient so that there is a greater pressure above the membrane than below.

Seawater begins to filter through the semipermeable membrane. Salts and sediment are left behind, and potable water comes out on the permeate side. The same pumps that created the pressure imbalance then send the drinkable water to shore in pipes.

One of the selling points of this deep-sea tech is that, compared to traditional desalination, it has a much smaller energy footprint—Flocean claims its process uses up to 30-50% less energy than traditional land-based desalination plants. Terrestrial desalination plants use energy to both pull water from the ocean and to push it through reverse osmosis membranes or heat the water for distillation.  

Deep-sea desalination doesn’t require either. In the deep sea, the ambient pressure of the environment pushes the water through the filter, whereas on land, pumps must create that pressure. Flocean only uses energy to pump potable water from the underwater pods to land. This process of transporting potable water to land also facilitates the pressure gradient that naturally draws seawater through the membrane in the first place.

Why deep water can be more predictable

In some ways, the environmental conditions of deep-sea desalination are also easier to work with than those here on land. For one thing, in the dark, where little light penetrates, photosynthesis cannot take place—plant matter is rare, and algae blooms are virtually impossible.

“It's quite boring in the deep sea—it's quite stable, and so it's predictable,” Alexander Fugelsang, CEO of Flocean, told Our Industrial Life. “And it's the only place where you can have a modularized, standardized desal plant, because it has the same pressure, the same salinity, the same temperature and predictable organics. [Whether] you're in the Mediterranean or the Red Sea or in the Indian Ocean, it's the same.”

The consistency and relative simplicity of the deep sea are important on several fronts: The lack of microorganisms and plant matter leads to less buildup in reverse osmosis membranes; they need less maintenance and remain functional for longer. The pods can also work in deep waters off any coast. Large desalination plants, on the other hand, require bespoke designs that take into account the unique biodiversity of the local seawater, the effects of floods, other natural disasters and potential algae blooms.

The complex environmental conditions are also costly and tend to extend permitting time. According to Fugelsang, it can take anywhere between 4 and 12 years to get permits approved and construction finished before standard desalination plants can start pumping clean water to municipalities.

While red tape can slow down larger projects, deep-sea desalination might be sped through permitting and deployment. Flocean, for example, which was founded in 2024, is already deploying a fleet of commercial pods off the coast in Norway. It expects to begin operations in 2026. Fugelsang emphasized that the technology lends itself to efficient permitting because of its minimal land use and environmental impacts.

“We were actually quite surprised at how smooth [the Norway] process went, but every country is different,” Fugelsang said. “So we are now trying to navigate and harmonize with the different permitting schemes in the EU and different parts of the world.”

Safe for the ocean: intake and brine

The modular, deep-sea desalination pods also don’t produce the super-salty brine characteristic of land-based desalination plants. On land, companies use energy for the entire desalination process, from sucking up seawater, delivering potable water to municipalities, to dumping brine. To make large plants viable, it’s important that they have high recovery rates. That means converting 35-45% of the seawater to potable water.

The downside is that the leftover brine is far more saline and often warmer than the nearby ocean water into which it’s released. The brine also might contain chemicals like chlorine from the pre-treatment process. As the natural salinity is altered, the water near the plant can become inhospitable for sea life.

Since the deep-sea filtration process is passive—the hydrostatic pressure of the deep sea does most of the work—Flocean pods collect between 15% and 20% of the seawater that enters the system, less than in traditional modern desalination. This means that the remaining brine is only mildly salty, and can diffuse into the surrounding area.

These lower recovery rates also help keep reverse osmosis membranes clean because the seawater that doesn’t filter through the membrane washes across it, collecting salty deposits before diffusing into the water nearby. The company estimates that the brine is sufficiently diffused within a 30-foot radius of each pod.

What will it take to scale subsea desalination?

The opportunities presented by deep-sea desalination have inspired multiple companies to develop their own technologies.

About four and a half miles off the coast of Malibu, California, another herd of water pods sits peacefully beneath the waves. Oceanwell, the California-based water startup, has a similar mission to Flocean: it aims to sustainably alleviate water scarcity in drought-strained regions.

By addressing the water needs of seaside communities, those that are much further inland may also see an improvement in their water resources. For example, Oceanwell hopes that with its commercial plant near Malibu, California will pull less water from the Colorado River, and thus free up water resources for states like Nevada and Arizona.