Sea serpent

The Sea serpent is an ocean going submarine owned by El Patético and used for their illicit operations. Primary function as a mobile command center but it is well armed.

Sea serpent by Jacob-W


Lower deck

Going from forward to aft on the lower deck, we first come across the main sonar, the air pressure tanks to blow the ballast tanks and the foldable bow planes. These are all situated outside of the pressure vessel, and are surrounded by the forepeak tank, used to trim the Sea serpent with ballast water.

Aft of that we come into the pressure hull of the ship, where we first have the messroom on the port and the galley and pantry on the starboard side. Then there is the double staircase leading up to the upperdeck. The staircase is separated by watertight doors. Aft of the staircase we find the Sickbay on the starboard side, then the Officer's quarters, and the Crew quarters on the port side.

The Missile hold, housing the six big ballistic missile launch tubes, cannot be accessed from the lower deck but it lays immediately aft of the living spaces. Followed by the engine room, also only accessible from the upper deck. Aft of the engine room lay the two separate rooms that house the electric motors used for the propulsion. Behind that is the battery hold and in the very end there is the after peak tank.

Upper deck

On the very forward, we first find the top section of the forepeak tank and the four torpedo tubes. Aft of that, the torpedo room where the launch crew works to load the torpedoes and a part of the torpedoes is stored. The torpedo room is closed by a watertight bulkhead. Aft of this is the forward missile hold. Housing the fourteen vertical missile launch tubes for the smaller SAM/SSM missiles, spare torpedoes, spare missiles, as well as other miscellaneous storage. This room has an (escape) hatch to the weather deck on top of the hull of the Sea serpent. This hatch is also used to load new torpedoes and other supplies, such as food. Also, this hatch is used to move the spare missiles from storage to the weather deck to load them into the launch tubes. The crew can do this at sea.

The forward missile hold is closed off with another watertight bulkhead leading into the staircase, and another watertight door leading to the bridge deck. This houses the command bridge, from where the Sea serpent is operated. The captain's cabin, his office, the radio room and the sonar room.

Behind the bridge-deck lays the missile hold, spanning both decks, with a walkway in between the six launch tubes leading into the engine room. Aft of the engine room we find the workshop with on the port side the air-conditioning room, and on the starboard the firefighting room. Aft again lays the air lock with (escape) hatch to the weather deck leading into the Remora if she is fitted. Or to the outside.

Behind Remora the hatch and towing installation for the towed sonar is fitted. Then we find the afterpeak tank, finishing off with a technical room with the actuators to control the X rudders.

Weather deck

The weather deck is the topside of the hull, all the hatches are constructed in such a way that they are flush with the deck when closed. Mooring gear such as bollards, chocks and fairleads are retractable into the deck to give the submarine a smooth hull when sailing under water.

Over both the forward and aft hatch, a davit can be rigged to hoist supplies in and out of the ship. Also, over the forward launch tubes, davits can be rigged to reload them.


The sail sits on top of the weather deck, and houses all kinds of equipment, such as the periscope and radio antennas. Also, a small lookout point is there for when the ship is sailing on the surface. The ship is still controlled from the bridge though, only communication equipment is placed on the lookout point to reach the command station.

Ballast tanks

Both in the forward and in the aft there are peak tanks fitted to control the trim of the Sea serpent On port and starboard of the pressure hull there are the main ballast tanks, split lengthwise in to four each. These tanks are used to control the deplacement of the submarine, allowing it to sink or surface. These main ballast tanks can be emptied with compressed air, stored into two tanks in the forward of the ship. The capacity of the air pressure tanks is enough to blow the complete main ballast tanks four times without the need for the compressor to fill them up.

Other tanks

The bottom of the Sea serpent is designed to work as a double bottom. Here fuel and fresh water is stored. As well as waste water, fresh and dirty oils. For obvious reasons, the tanks underneath the launch tubes aren't used for fuel, but are additional ballast tanks to regulate the stability by influencing the point of gravity of the ship.

As you can see my model is unfinished.
The software crashed on me three days before the deadline.
I have to thank Sh4d0wPh03n1x for helping me safe an old file, and being able to show atleast half the model.
Owning Organization
Only known of one in existance
15 meter (49 feet)
110 meter (360 feet)
15 meter (49 feet)
10.000 tons (submerged)
15 knots on the surface / 35 knots submerged
Complement / Crew
10 officers and 20 ratings
Cargo & Passenger Capacity
20 passengers
6 balastic missles
14 SAM/SSM +10 spare
32 torpedoes
10.000 nm using the diesel engines
5.000 nm using the batteries at 15 knots
1.000 nm using the batteries at full speed
"Kapitänin?" Mr. Fisher asked.
-"Ja, was ist los?" Rose replied.
Fisher was standing at the stern of the Sunset Dawn looking out over the water as he tends to do in the rare moments he went on deck.
"Wir werden verfolgt."
-"Was? Wo, ich sehe nichts am Horizont."
"Nicht auf dem Wasser, aber darunter." Fisher replied with a smile.
-"Hast du ein Periskop gesehen?" Rose asked surprised.
"Nein" Fisher paused for a moment. "Uns folgen zwei wellen."
-"Waves? We are followed by waves?"
"Sie segeln zu nahe an der Oberfläche. Schon zwei tage."
"-Was sollen wir damit machen?"
"Ignorieren." Fisher leaned over the bulwark drumming his fingers. "Wir wissen nicht, was sie wissen. Jetzt sind wir nur touristen.

General Arrangement submarine 'Sea serpent'

Power & Propulsion


The Sea serpent is equipped with two variable pitch propellors driven by independed electric motors. These motors are powered from the batteries or directly from the main diesel generators when sailing on the surface or at snorkel depth.

Both the pitch and the rotation speed is regulated from the bridge, independed or controlled by the computer to match the ideal pitch and rpm to the current speed trough the water.


The Sea serpent is equipped with two main diesel generators and one auxiliary diesel generator.

The main diesel generators produce 10.000 kW (12.500 kVA) each at 3~ 440 V.

The main diesel generators are used to propel the ship and supply power to everything else while traveling on the surface. The auxiliary generator is used in port, at anchor, or when floating offshore. It cannot be used to drive the electromotors that propel the ship directly, but it can be used to charge the batteries.

The auxiliary diesel generator produces 850 kW (1060 kVA) each at 3~440 V.

Sea serpent by Jacob-W (render by ShadowPhoenix)


On the sail, one can also find several radio antennas and the satellite communication disc. Covering all possibilities. All those are retractable into the sail for underwater operations.

Sea serpent main engines by Jacob-W (render by ShadowPhoenix)

Weapons & Armour

Aft of the sail, there are six vertical missile tubes, housing six ballastic missiles, one in each. The missiles can be launched while at the surface and while submerged up until operational depth. Normally the tubes are sealed air and watertight, and prior to launching they are flooded with outboard water and the hatch on top opened.

Forward of the sail there are fourteen vertical missile launch tubes for SAM/SSM missiles. These missiles can be launched while the submarine is at the surface and while it is submerged up until 100 meters of depth. The tubes can be reloaded by the crew, unlike the ballistic missiles which require a shore crane. A davit can be rigged over the forward hatch and over the launch tubes and this way spare missiles can be loaded in the tubes, even while at sea if the weather allows.

In the bow, there are four forward facing horizontal torpedo tubes. In the torpedo room there are twelve torpedos on standby. Five on each side in the racks, and one on each loading lift. There are an additional twenty torpedos in secondary storage.

The Sea serpent is unarmoured, it's defense is to go unnoticed, and everything is done to improve the chances of that happening.

Sea serpent missile launch tubes by Jacob-W (render by ShadowPhoenix)



In the bow of the Sea serpent the main sonar is fitted under the torpedo room, capable of both active and passive operations in multiple frequencies. In combination with the side sonar arrays, it can also look upwards.

Along both sides of the hull, there are sonar arrays. Over the length of thirty meters, they are placed halfway up the hull on the parallel sides. Running for-and-aft. These multi-beam multi-frequency side-scan sonars can be both active and passive. Active they can make pictures of the sea floor under the Sea serpent as well as things above and to the side of the submarine. Passive they can very precisely pinpoint the origin of a sound because of their long length.

In passive mode, if a sound source is identified and located, the computers of the Sea serpent can produce images of the surroundings with the ping of another source and how the echoes are received by the Sea serpent.

In addition, there is also a towed sonar, a small hatch in the stern of the Sea serpent can deploy a sonar bulb on a 2500 meter line. This creates a gigantic antenna which highly enhances the accuracy. Also by putting the towed sonar to active, and the hull mounted sonars to passive, potential enemies can be fooled into thinking the Sea serpent is more than a mile away from the actual location.

Sail mounted sensors

In and on the sail are several sensors, most of which only useable above water. The periscope is the best known instrument, it primarily is a tool to view above the water service while sailing just below it. It is equipped with build in compass, sextant, magnifiers, camera, infrared camera, range finder. The periscope is lowered and raised with hydraulic power, and is built strongly to withstand the pull of the water when the submarine is moving.

Also there is a radar scanner and the electrical warfare mast. The radar is there to find surface or air targets for navigation or hunting purposes. The electrical warfare mast is equipped with sensitive radio and other electronical signals sensors, capable of determining the direction of the origin and the range. Also, it is capable of sending jamming signals in multiple frequencies. The radar and e-warfare mast can only be deployed when the whole sail is out of the water, and are retracted into the sail before the Sea serpent dives.

Sea serpent by Jacob-W (render by ShadowPhoenix)

Auxiliary systems


On the aft of the sail the snorkel is fitted, this is an air supply pipe for the engines, that is extendable the same as the periscope, and it can be deployed while sailing at periscope depth. This way the Sea serpent can run her main diesel generators while sailing under water.

Just aft of the snorkel are the exhausts of the engines fitted also extendable to above the waterline while sailing at periscope depth.

Control surfaces

The Sea serpent is built with X rudder on the stern, instead of the traditional + rudder and rear stabilizer arrangement. The X rudder requires more tech to operate the flaps, as they need to move independently from each other. But they can be longer than their + arranged counterparts. They fill the diagonal of the square space the hull takes in. With the X arranged rudders being longer, they can be thinner and all in all have less surface area, create less drag and be quiter.X rudders also aid in the manoeuverability as all four are used to change course or change depth. Also, because the rudders are longer, their control surfaces can be shorter for the same surface area.

In the front of the Sea serpent bow planes are fitted, together with the X rudder on the stern, they control the depth and pitch of the ship. The bow planes are foldable into the hull as they protrude out beyond the side of the hull. This allows for mooring and better surface sailing.


The submarine is fitted with an air-conditioning system that uses an elaborate washing installation to take the carbon out of the CO2 and refresh the air for the living spaces with oxygen. Aswell as the necessary heating and cooling. This system allows the submarine to stay submerged for three months.

Fire fighting

To fight fire, the Sea serpent is fitted with a CO2 suppression system for the engine room, forward and aft missile holds and the torpedo room. In case of fire, these spaces can be flooded with CO2 to deprive the fire from oxygen and extinguish it. All other living spaces are protected by high fog sprinklers, drawing water from the fresh water tanks.


On the back of the Sea serpent a secondary small submarine is carried, named Remora. Attached to the aft hatch with a watertight seal so that the crew can move from one to the other.

Remora is a fully electric submarine, which can house eight people, and is generally operated by two crew members but can be sailed single-handed. It does not have any armament, but is equipped with two mechanic arms and space to store items in a compartment under the hull or on the side of the submarine.

The name Remora comes from the fish with the same name that sucks itself to bigger fish to hitch a ride.

Cover image: by Johannes Plenio


Author's Notes

This article was made for The Shipwright Challenge.

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25 Sep, 2021 10:58

Very cool

29 Sep, 2021 17:47

Thank you

29 Sep, 2021 23:08

As someone who served on submarines, very well researched and thought out article. there were only a few things that i saw missing: 1. A fan room (usually near the sail, allows fresh air to be brought on board and circulates air throughout the ship. 2. Oxygen generation and storage/CO2 recycling and atmospheric monitoring. its a closed environment, so its important for people to know how long they can keep breathing and if there are any detectable toxic gasses 3. fire suppression systems - there are a lot of flammable things, being able to put out a fire quickly and safely is vital. 4. battery capacity and how long the ship can stay submerged. the battery capacity can be a range, I would include a max speed capacity and a max battery life capacity.   also, typically on a submarine with a sail the height will be greater than the beam, due to the sail being included in the height.   overall very well done, cant wait to read the finished product.

As always, it would be appreciated if you would stop by my challenge article The Storm Giant Empire and leave some feedback.   If you are looking for things to read from summer camp there is also my Summer Camp 2022 Reading Challenge.. Happy worldbuilding.
1 Oct, 2021 12:19

I've to be honest I did not expect to have a submariner read my article, so that you like it makes me really happy.
I've taken your points into account and made some additions. Writing this and building went hand in hand, and the air-conditioning was on my mind. How I completely missed the fire fighting part, as it is my job to look after it at the ships I work on, is beyond me. Unfortunately my model crashed yesterday, and I lost most of the work on the aftside. For the height yeah, well I just build what felt right, and measured that. So the outer hull isn't really round.

1 Oct, 2021 17:22

Very well done on the map and design. There are a few things that I might have switched around if i was doing it, but as I havent researched too much in to submarines besides the ones i served on. I dont see anything that i see as "this would break the boat/kill everyone" like I said, great job. only thing that really stood out can be written off as "its included in the quarters," is that there are no bathrooms on your map.

As always, it would be appreciated if you would stop by my challenge article The Storm Giant Empire and leave some feedback.   If you are looking for things to read from summer camp there is also my Summer Camp 2022 Reading Challenge.. Happy worldbuilding.
2 Oct, 2021 10:53

Toillets? yes, of course they are in the quarters..... oops.

2 Oct, 2021 14:47

That's a unique way to go about making your map. I liked it.   Was the model entirely virtual or did you physically piece it together?

3 Oct, 2021 07:13

Thank you. I'ts only virtual, I don't have that many Lego bricks :D. I used to make it.

Eternal Sage AmélieIS
Amélie I. S. Debruyne
3 Oct, 2021 11:58

Great article, I really love all the technical details and learning more about submarines :D A shame the model crashed but I really like being able to see th submarine in 3D.   I was a bit slow reading everything because of all the English vocabulary I'm not used to - I don't even think that counts as technical terms that should be tooltiped, so nothing you can do about that.   Only things that you might want to add are what "trim" means for a submarine, and that the sail in submarine is not the same as in sailing ship but that it's the extension it has on top (though I ended up figuring that one on my own :p ).   Also, you didn't state in directly but I can infer it: the diesel motor cannot be used below a certain depth because it needs to extend it's tubes to the surface, but while it's used it can replenish the battery, and the battery is then what is used to move the propeller below that depth. So that means the submarine as to resurface regularly to replenish the battery even if the oxygen is still there, is that correct? I think you can develop that a bit more to clarify.

To see what I am up to, here is my civilisation challenge article.
3 Oct, 2021 12:15

Thank you Amélie. It's actually quite difficult to write about a subject you know (too) much about, and trying to not go too deep into jargon so that 'normal' :P people it still understand.

Trim is the angle of the ship along the length. So if the bow is facing up or down.

Correct the engines can only run when the submarine is sailing on the surface, there they charge the batteries. Or when sailing at periscope depth, just below the surface. when they take in air via the snorkel. When diving deeper they run on the batteries alone. I did specify the range on the batteries above.

Eternal Sage AmélieIS
Amélie I. S. Debruyne
3 Oct, 2021 14:16

I'm guessing that the batteries cannot be on constantly or they would run out before the oxygen, right? Do you know vaguely how many hours of activation at 15 knots or full speed this would correspond to? Just so that I can compare that to the months of oxygen available.

To see what I am up to, here is my civilisation challenge article.
3 Oct, 2021 18:50

The range on the batteries is 5.000 nm, at 15 knots. That's 14 days.
At full speed 35 knots, the range is only 1.000 nm. That is 28 hours.
To put the distance into perspective. Crossing the Atlantic, Le Havre -> New York is 3.600 nm.
So yes they run out of battery juice before the oxygen for human consumption runs out.
But a submarines life isn't spend crossing the ocean at full speeds, it is sneaking and hiding at the enemies coast. So those 3 months of air for human consumption, isn't necesary spend moving.
Those numbers are my educated guess, that kind of information of real submarines is difficult to find as Navies try to keep that a secret. But based on the size you can assume a quantity of fuel, and knowing engines you can make a range, etc.
The diesel engines cannot run underwater, there is noway that it's technologically feasible to have a system that produces enough air for the engines to work on in a realistic way, and you have to get rid of the exhaust. There are systems of running a diesel engine underwater, but you have to carry liquid oxygen and all kinds of systems, I wanted to keep it simple.

Eternal Sage AmélieIS
Amélie I. S. Debruyne
3 Oct, 2021 20:13

Thanks for the estimation, that was what I was wondering about :D

To see what I am up to, here is my civilisation challenge article.
4 Oct, 2021 14:34

Ooo a submarine. You can tell you know a lot about the subject from the way you've written the article. Very interesting, and I love the model! :D   I would love a translation of the conversation in the side bar.   Great job!

4 Oct, 2021 20:48

Thank you Emy!
But Mr. Fisher doesn't know (refuses to use) English :D.
I'll put a variable thingy with a translation under it, as I'm toeing the word count limit.

4 Oct, 2021 22:45

Thank you! <3

Sage eccbooks
E. Christopher Clark
5 Oct, 2021 12:37

The level of detail here is awe-inspiring. I was sorry to hear about your troubles with the model and rendering, but I never would have known. Everything here comes together so well.

Check out my article for the 2022 Summer Camp Reading Challenge
5 Oct, 2021 14:47

Thank you :)