La Chambre Bleue

An underwater habitat for living on a coral reef, held at sea-level pressure and independent of the surface. Designed 2022–2023.

Rendering of the habitat on a sandy patch between coral: two transparent acrylic modules angle out from a central steel module, with two steel modules behind.

The habitat was designed so that a small group could live on a reef for weeks at a time, in comfort and safety, with the sea on the other side of the wall. It is unusually large for an undersea habitat: about 260 m³ inside, more than twice the volume of the Aquarius reef laboratory, with two nine-metre living modules made of clear acrylic. Through 2022 and 2023 a team of submarine, life-support and electrical engineers, a marine scientist and an architecture studio took it from concept to detailed systems design, built a scrubber prototype and tested solar panels at sea.

Site depth: 10–15 m
Interior pressure: 1 atm
Extended stay: 5 people, 14 days
Short stay: 25 people, 3 days
Interior volume: about 260 m³
Acrylic hull area: about 180 m²

Key contributions

Earlier seabed habitats kept their crews at the pressure of the water around them. La Chambre Bleue holds sea-level pressure on a shallow reef, so divers and non-divers can live for weeks in clear acrylic rooms, independent of the surface, and leave without decompression.

01

A one-atmosphere habitat at 10–15 m

Most habitats since Conshelf have been held at the surrounding water pressure so that divers can saturate. This one keeps its interior at sea-level pressure, like a submarine fixed to the seabed, so occupants can stay for weeks and leave without decompression.
Chapters 01, 05
02

Cast-acrylic living modules

The two living modules are nine-metre cast-acrylic cylinders, set around a patch of reef so that the rooms look out on it from every side. A cleaning mechanism running along each hull keeps the view clear.
Chapters 01, 11
03

No connection to the surface

There is no umbilical, buoy or shore link. A battery bank sized for fourteen days, oxygen stored on the seabed and an onboard watermaker carry the habitat between fortnightly visits from its support vessel. For emergencies it can deploy a buoy carrying satellite communications.
Chapters 04, 06, 07
04

A one-atmosphere transfer bell

An unpowered bell docks to the habitat and carries up to five people or a load of cargo at surface pressure, so guests who cannot dive can visit, and equipment that must stay dry arrives dry.
Chapter 05
05

Underwater solar power

A draft design for solar panels mounted on the habitat at its own depth, to stretch the time between recharges. To size it, the team built an instrumented rig and measured panel output at 5, 8 and 11 m off Anilao, in the Philippines.
Chapters 04, 12
06

Interiors for long stays

The cylinders are designed as places to live rather than work: suspended nets, sleeping spaces at several heights and reconfigurable floors, for five people over two weeks or twenty-five over a weekend.
Chapters 02, 03

General arrangement

Five modules joined by two junctions. Every module can be sealed from the others.

Labelled plan: dive centre and moonpool at upper left, machinery at upper right, central kitchen and library across the middle, shared module at lower left in blue and private module at lower right in red. — General arrangement

Shared module: AcrylicGathering, dining and lounging, with open floor for standing events. Sleeps a large group for a weekend.
Private module: AcrylicSleeping spaces at several heights, with private rooms for longer stays.
Central module: SteelKitchen and library, with three large viewports.
Machinery module: SteelBathrooms, machine room and a sealed battery compartment.
Dive module: SteelMoonpool room, primary and auxiliary airlocks, and the docking port for the transfer bell.

Part I

Structure and interiors

Shell, frame and ballast

Every module is a pressure hull. The interior stays at one atmosphere while the sea presses in, so the structure was engineered to the safety margin used for crewed submersibles. Each module sits on a steel frame over concrete ballast: an acrylic module displaces about 66 tonnes and needs roughly 78 tonnes of concrete to hold it down.

Displacement, acrylic module: about 66 t
Ballast, acrylic module: about 78 t

Oblique rendering of the five-module habitat, with transparent acrylic wings. — Fig. 1.1Exterior model

Top view of the Y-shaped habitat with two parallel steel service modules. — Fig. 1.2Structure, plan view

Render of the complete structural assembly with ballast blocks. — Fig. 1.3Complete assembly

Render of the steel support frame under an acrylic module, from the assembly model. — Fig. 1.4Module support frame

Interiors of the acrylic modules

The interior concept, developed with the architecture studio LIQUIFER, treats each cylinder as one continuous room. The shared module has a convertible floor, drop-down tables and a suspended net; the private module stacks sleeping spaces at different heights so that the whole volume is used. The brief asked for dark, cool colours with warm accents, tile and mosaic, and plants, and ruled out anything futuristic or nautical.

Shared module

3D model of shared seating, tables and a suspended net. — Fig. 2.2Shared module, 3D study

Dimensioned floor plan of the shared module. — Fig. 2.3Shared module, floor plan

Circular section through the acrylic module with furniture. — Fig. 2.4Shared module, transverse section

Four 3D studies of table placement and floor levels. — Fig. 2.5Table and floor arrangements

Private module

3D model showing private spaces at several heights inside the acrylic cylinder. — Fig. 2.7Private module, 3D study

Dimensioned plan of the private sleeping spaces. — Fig. 2.8Private module, floor plan

Cross section of the private module, showing spaces at different heights. — Fig. 2.9Private module, transverse section

Four 3D studies of hanging and separate sleeping pods. — Fig. 2.10Sleeping arrangements

Kitchen, library and bathrooms

The steel central module holds the kitchen and a library that follows the curve of the hull; the machinery module holds one full and one half bathroom.

Illustrated cutaway of the library shelves, seating and kitchen counter. — Fig. 3.1Library and kitchen

Cutaway model of the kitchen counter, dining nook, storage and refrigerator. — Fig. 3.2Kitchen and dining

Model section through toilets, shower and hand basins. — Fig. 3.3Bathroom arrangement study

Cutaway model of an acrylic module with sunken seating and suspended lights. — Fig. 3.4Lounge and lighting in an acrylic module

Part II

Life-critical systems

Machinery and electrical power

With no cable to shore, everything runs from a lithium iron phosphate battery bank behind a sealed bulkhead. The bank is split into two independent halves, so a single fault costs at most half the capacity, and every module has its own backup battery for life support. The support vessel recharges the bank on each visit.

Cutaway model of equipment racks, batteries and dive-centre equipment. — Fig. 4.1Machinery and dive modules

Cutaway equipment layout showing service access around tanks and machinery. — Fig. 4.2Equipment and access clearances

Diagram of charging, batteries, inverters and electrical distribution. — Fig. 4.3Electrical distribution schematic

Energy-storage sizing study

Average load	1.2 kW	Usable fraction of capacity	70%
Autonomy target	14 days	Charging power from vessel	80 kW
Calculated storage	576 kWh	Calculated charging time	7.2 h

Average loads in the power study include 240 W for interior lighting, 175 W for exterior lighting and 119 W for dehumidification.

Dive centre, airlocks and transfer bell

Divers surface into the moonpool room, which is open to the sea at ambient pressure, then pass through an airlock to the one-atmosphere interior. The airlock is designed to work with the electrical power off. An auxiliary airlock alongside can be joined to it to move more people or larger equipment. Together the two hold twenty-five people, the habitat's full short-stay capacity, and the auxiliary airlock has its own escape hatch. The transfer bell docks on top for people and cargo that should not get wet.

Model looking along the dive centre, past the moonpool opening and stored cylinders to the airlock. — Fig. 5.1Dive centre and airlock

Plan view showing the dive-centre access sequence and airlock. — Fig. 5.2Dive centre, sectioned plan

Render of the transfer bell and its viewport. — Fig. 5.3Transfer bell

Model section showing the transfer bell above its docking connection to the habitat. — Fig. 5.4Transfer bell docked, section

Airlock pressure-system schematic. — Fig. 5.5Airlock pressure circuit, revision 2.0

Airlock vacuum-system schematic. — Fig. 5.6Airlock vacuum circuit, revision 2.0

Air and life support

Each module has two independent environmental-control sets that swap roles every eight hours, so the backup is always known to work. Oxygen is added from banks stored outside on the seabed, which keeps pressurised oxygen out of the living space. Carbon dioxide is removed by fan-driven soda-lime scrubbers, and filters and dehumidifiers clean the air. Critical sensors are duplicated and have their own batteries. A quarter-scale scrubber was built and instrumented for bench testing.

Pressure: 1 atm ± 1.7%
Oxygen: 18–23%
CO₂ limit: 5,000 ppm
CO₂ target: 1,000 ppm
Oxygen reserve: 14 days + 50%

System diagram showing oxygen addition, CO2 scrubbing, air quality, temperature and humidity monitoring. — Fig. 6.1Per-module environmental control

Assembled model of the scrubber prototype and its housing. — Fig. 6.2Carbon dioxide scrubber prototype, assembly model

Photograph of the scrubber test bench with gas supply, instrumentation and a laptop. — Fig. 6.3Carbon dioxide scrubber test bench

Fresh water and waste

A watermaker desalinates seawater, which is filtered and sterilised with ultraviolet light before use. Showers can switch to seawater to save fresh water. Grey water from sinks and showers is filtered and reused to flush toilets; black water is ground and held until the support vessel takes it ashore.

Freshwater system drawing showing watermaking, filtration, disinfection, storage and distribution. — Fig. 7.1Freshwater system, revision 1.1

Waste handling

Showers and sinks
Internal grey-water tank
Filtration and toilet flushingSeawater as an alternative flushing supply
Grinder and pump
External black-water bladder
Support vessel to a treatment facility

Transcribed from the waste-system overview.

Wastewater drawing with grey-water filtration, toilet plumbing and tanks. — Fig. 7.2Wastewater plumbing

Sensors, network and control

Three monitoring stations share sensor data over the habitat network, so the loss of one does not blind the others, and report to a central control station that keeps an event log.

Diagram: six habitat systems, each through a bridge if needed, are read by three monitoring stations, which read each other and push events to the control centre. — Fig. 8.1Monitoring network, topology

Diagram of the control centre and monitoring station in the centre module, a monitoring station in the other modules, the battery management system and the links between them. — Fig. 8.2Monitoring network, architecture

Both diagrams are redrawn from the original network design.

Fire and emergency systems

Every system is designed to tolerate any single fault. Fires are detected by multi-spectrum infrared flame detectors, smoke detectors and gas analysers, and fought with water-mist and CO₂ extinguishers, sprinklers, and nitrogen flooding for the battery compartment. Every occupant has an emergency breathing apparatus. Because the interior is at one atmosphere, escape is a free ascent of ten to fifteen metres with no decompression.

Habitat drawing with fire-system device locations and connections. — Fig. 9.1Fire detection and control, layout study

Photograph of the emergency breathing apparatus mock-up. — Fig. 9.2Emergency breathing apparatus, mock-up

Diagram of the sprinkler distribution to habitat compartments. — Fig. 9.3Sprinkler branches to each compartment

Part III

Installation and upkeep

Support vessels and installation

The modules are ballasted in a dry dock, floated to site on a partly submerged barge, and winched down onto galvanised steel base frames that divers assemble and level on the seabed. A landing-craft support vessel visits every two weeks to recharge the batteries, refill oxygen, remove waste and bring people and supplies.

Two models of support vessels, showing machinery blocks and a winch. — Fig. 10.1Support-vessel arrangement studies

Model rendering showing ballast blocks and adjustable screw supports. — Fig. 10.2Ballast and seabed supports

Stage 1Float each module to site on a partly submerged barge
Stage 2Lower, position and level the seabed frames
Stage 3Winch the slightly buoyant modules down onto the frames

Site-selection criteria

Reef and water

Reef structure, biodiversity, clarity and currents.

Conditions

Storm exposure and local environmental conditions.

Access and support

Ports, crane capacity, parts, labour and community support.

Keeping the acrylic clear

Marine growth on the acrylic slowly takes away the view. A light steel frame around each cylinder carries a cleaning mechanism that travels along the hull.

CAD view of the acrylic cylinder and its longitudinal cleaning mechanism. — Fig. 11.1Acrylic cleaning mechanism, model study

Hand-drawn routing of the cleaning mechanism. — Fig. 11.2Cleaning mechanism, drive-path sketch

Underwater solar power

The electrical design includes a solar branch that charges the battery bank in addition to the support vessel. Light fades quickly with depth, so the team built an instrumented rig and lowered monocrystalline and amorphous panels to 5, 8 and 11 m off Anilao, in the Philippines, to measure what a panel at habitat depth would produce. Extrapolated to a full day, the measurements give about 117 Wh per square metre at 5 m, 69 at 8 m and 47 at 11 m. At 8 m, covering the habitat’s daily use of about 29 kWh takes roughly 420 square metres of panel, so the array’s job is to reduce how often the habitat needs recharging. The draft array sits on the roof of the central module.

Full-day yield, 5 m: 117 Wh/m²
8 m: 69 Wh/m²
11 m: 47 Wh/m²
Area for 29 kWh/day at 8 m: about 420 m²

CAD rendering of the habitat with a solar array on the roof of the central module. — Fig. 12.1Draft roof-mounted solar array

Photograph of the solar panel and measurement electronics before deployment. — Fig. 12.2Panel and logging electronics before deployment

Photograph of the solar panel and frame during the underwater test. — Fig. 12.3Test panel in the water

Underwater photograph of the experimental panel and suspended measurement rig. — Fig. 12.4Suspended test rig

Plot of measured depth and estimated panel power during the experiment. — Fig. 12.5Measured depth and estimated panel power

Plot comparing extrapolated full-day solar generation at 5, 8 and 11 m. — Fig. 12.6Extrapolated full-day generation at three depths

La Chambre Bleue

A one-atmosphere habitat at 10–15 m

Cast-acrylic living modules

No connection to the surface