| building of an underwater room |

• how do you start

I suggest to build it on the watersurface as craning a whole room with windows looks like a manouver that would in practice probably cost more than building the room itself.

Second it is expensive and complicated to get a building place on the waterfront of the required size in any marina and shipyard as the waterfront is the bottleneck of the whole operation.

The idea to have a room of hundreds of tons sitting there during months of building and then sourround it with heavy cranes that can lift and move it with beams large enough to reach out on the watersurface is nightmarish at least…especially if you pretend to keep up operations with fragile white shiny glasfiber yacht around it.

So it is best to build on the watersurface where you have plenty of space and do not interfere with other operations that need the high value waterfront. (context)

There is a good reason why oil platforms are no longer built on land - and then floated out…as you see it in the context images.

Lets take this image as a “frame paradigm” what we mean when talking about an underwater room"

Be aware that what the picture shows is a air volume of maybe 600 tons and above so to get it underwater you need a weight of 600 tons…that is not a thing you can move around on land or transition from land to water. Like a whale it must be born (built) in the water, while supported by water, and stay supported by water for all its lifetime.

So something that has a generous size and is clearly out of the range of craning and moving it around on land.


It also implies that it can not be “taken out of the water” like boats yachts and ships - not even in a big, specialized, and expensive, installation like a drydock

Therefore the acrylic windows that come to mind first, are not a very good option as they scratch easy, can be completly ruined with the wrong cleaning product, tend to age poorley.

There is a good reason why acrylic is NEVER used for windows in buildings like skyscrapers. It only looks good for a few months - not good enough for real estate where you want to “sell the view” for decades to come.

What you want to avoid is a situation where you have a room that you can not take out of the water but the windows have become ugly and you have no way to replace them.

So it is convenient to go for something that has a good durability record.

Imagine you send a diver down there to clean the windows - what you need to do every second day - and a small shell creature on the window gets squashed and leaves a mayor scratch clearly visibe, every single time you do the process.

So in practice you perfer laminated glass windows - what leaves you with the option of bus windows.

The building strategy is not designing the room and then custom fabricate the windows for it - it is better the other way round - get the windows - for example a dozend bus front windows and then build the room to provide a frame for those windows.

context : the case for bus windows

The room has 3 parts


This 3 part strategy is the base to get something that is unsinkable even if one of the windows should break

Imagine the room is full of people and then it starts not only flooding quickly but simultaneysly sinking as the water pouring in adds to to the weight and eats up buoyancy.

The minimum you need is that the flooded room stays on the surface and people can escape to the top floating body easyly.


building of an oil platform | you have the floating nucleus of the platform itself and workshops on barges surrounding it | stuff like building materials is floated in on demand |

So how do you apply this on a smaller scale for an underwater room ?

• Step1 | Building a “floating nucleus” where you can set shop on

In the finished build the nucleus becomes the concrete ballast plate that gives the weight to overcome the buoyancy of the window room and the air it holds - but at the beginning you want it floating on the surface and light so you can set shop on it , work and stand there while you build.


This is me (@nautilusmaker ) doing a an assembly of floating cubes 1m each in cartagena | the wall thickness of the cubes is 5 cm.


A light waffle shell type floating nucleus where the wall thickness is only 5mm from laminated advanced cement composite | this thing sinks only 2 cm into the water | it was built by my team in Cartagena.

Some variations of building the floating nucleus are on the table ( i will detail here )

When all is set and done you end up with a floating (honeycomb) slab that is ready to recieve the next step : the window room - columns and windows…


picture the floating slab that is reforced and ready to get the weight increase something like this…

you might go for a top plate on the honeycomb slab, to get a good standing surface for the further construction. In the later state the slab will not be very different from what you see in a off the shelf land construction.


floating slabs type caission unloaded for a land extension in monaco - this is pretty much the old mulberry harbor technology


a floating slab of roughly room size


construction steel for connecting the columns sticking out


| a top plate on the honeycomb structure facilitates standing and further work logistics |

• Step 2 - Columns and Windows - the Window Room


what comes on top of the baseplate is concrete colums in the distance given by the windows you have available.

(Again the design evolves around the windows you can get )

The windows go in slits in the colums (cast in a poolnoodle) that can easyly be removed from the hardened concrete and leave a slit.


Buswindows are normally attached to a bus chassis with this kind of rubber seals - those seals are watertight so you have two options

• Put the seal on the window put the assembly into the slit of the colums and grout it in .
• Cast the window in without a rubber seal

both will work


Windows of enourmous size and more than 1m thickness have been performed already.

• The acrylic is hold in place by concrete colums it is of essence to keep the contact surface between acrylic and concrete flat to avoid stress points and cracking in the panel.

• Those windows figure among the most expensive windows on the planet due to the complicated process of fabricating clear optical acrylics of that size.

once you have your assembly of concrete colums and windows built you get something like the picture above. The only difference - your column window assembly is standing on a light floating platform and there is A LOT of weight necessary to bring it down to the point where you can “see the ocean trough the windows”.

So you start to enforce the baseplate ( that was your floating nucleus ) to recieve this enormous increase in weight . You use concrete beams and standard rebar to do so. Then you start to fill more concrete into the cells to get even more weight.

The good thing is this adding of enourmous weight goes very gradual at no moment there happens something spectacular that involves heavy lifting. The weight comes in one bucket load at a time . The platform sinks down millimeter for millimeter and if you find a leaking seal somewhere you can easyly access and repair it .

The building of the top plate (closing the window room above) starts very much like the column / slab construction usual in land building. You get a standard scaffolding for plate building


this comes in standard room height - means it fits perfectly - and gives you the forming for casting the top plate.

On top of that scaffolding you cast the top plate | now you have a new area to stand on and to use as the base for construction of your upper floating body.


fish will tend to circulate the structure and concentrate in the somewhat protected space beneath the floating upper body and the windows - means they tend to stay exactly in front of the windows - especially if you mount underwater lights that attract plankton for food.

Step 3 • The floating body | top building | unsinkability | buoyancy |

The floating body has the function to provide “reserve buoyancy” in case things go south and a window breaks flooding the underwater window room. The buoyancy of the floating body prevents sinking of the structure.

The floating body also provides a platform to load and unload people, have some additional infrastructure etc…

It is light made in honeycomb structure or in Floating-Rock™ .

| floating rock | advanced cement composite | seasteading |

It could also be made out of foam (like a surfboard) etc…


something like this…

• At no time in the whole construction process you need more than 2 people working on the site

• At no time you need heavy construction cranes or other construction equipment - you will be fine with the mixer and shovel setup you see in family home building sites.


• It is no big deal for a 2 man team to create 5 cubic meter of concrete per day with these tools.

• This means you get a progress of roughly 12 tons per day in this simple setup.

• A 500 cubic meter room cooks down to a 40 workday project…

• Building something compareable in marine steel cost at least 4 times more and gives you 10 times less service life expectancy.

• Space and infrastructure requirement in the marina is minimum ( an electric shoreside connetion would be great )

questions left ? | contact info@tolimared.com | and start a conversation

This construction technology sounds outlandisch to you ? Look what else we have done already.…(building of a submarine yacht).

Floating Diagrid Structures

The principle of basket weave applied to Seasteading

Floating Light Honeycomb Shell Structures

Light oceanic construction

Bubble Cluster Structure Seasteading

Multiple spheres, domes, acting like a giant foam block

Ocean Sphere

The Sphere is the most efficient shape for large scale enclosure of human living space in hostile environments, it allows the most volume with the least material in the structural toughest way.

Plate Seastead

| Stadion Seastead | Lens Seastead |

Ramform Seastead

The need for a bow on a oceanic structure under 400m

questions left ? | contact info@tolimared.com | and start a conversation

This construction technology sounds outlandisch to you ? Look what else we have done already.…(building of a submarine yacht).

What we are currently talking about with the ocean building community in general.

glass bottom boat underwater room