> For the complete documentation index, see [llms.txt](https://create-deep-seas.gitbook.io/create-deep-seas-wiki/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://create-deep-seas.gitbook.io/create-deep-seas-wiki/getting-started/your-first-submarine.md).

# Your first submarine

This page walks you through a small working submarine, from the hull to the first dive. Every block has its own page with the details, this is just the order things go in.

## 1. The hull

Build a closed hull with no holes, in whatever shape you like. Any solid block works, but each material has its own depth limit: glass breaks at 20 to 30 m, wood around 40 m, stone 60 to 80 m and iron around 100 m. For windows that hold deep, use [Pressurized Glass](/create-deep-seas-wiki/deep-seas/hull/pressurized-glass.md).

The shape matters too. With the default pressure model, a big flat wall holds less than a small rounded cabin made of the same blocks. See [Water pressure](/create-deep-seas-wiki/deep-seas/mechanics/water-pressure.md).

{% hint style="warning" %}
Open doors, trapdoors and fence gates count as holes. Close them before diving. If the hull does not seal, the Diagnostic page of the [Onboard Computer](/create-deep-seas-wiki/deep-seas/diving/onboard-computer.md) lists every leak.
{% endhint %}

## 2. The ballast

The submarine goes up and down by filling its ballast with sea water.

1. Place [Submarine Ballast Tanks](/create-deep-seas-wiki/deep-seas/diving/ballast-tank.md) inside the hull. One tank for every 75 blocks of submarine is enough, no more.
2. Place a [Ballast Vent](/create-deep-seas-wiki/deep-seas/diving/ballast-vent.md) with at least one face touching the sea.
3. Pipe the vent to the tanks through a pump.

{% hint style="danger" %}
**Use as few Ballast Tanks as possible, and as many Pump Controllers as you can, on a fast shaft (256 RPM).** Every tank is 8 more buckets to pump in and out. Too many tanks with too few or slow pumps, and the submarine takes ages to dive and to climb back up.
{% endhint %}

A pump pulling from the vent fills the tanks and the submarine dives. Turn it around and it pushes the water back out: the tanks empty and the submarine rises.

For a submarine that holds its depth on its own, use a [Pump Controller](/create-deep-seas-wiki/deep-seas/diving/pump-controller.md) instead of the plain pump and add an [Onboard Computer](/create-deep-seas-wiki/deep-seas/diving/onboard-computer.md). You then type a depth on the screen and the computer does the rest.

## 3. Air

A sealed hull keeps the sea out, but the crew still needs air once it dives.

1. An [Electrolyzer](/create-deep-seas-wiki/deep-seas/air/electrolyzer.md) turns water into oxygen. It runs on FE, or on rotation with a Shaft in its module slot.
2. Pipe its oxygen to an [Oxygen Diffuser](/create-deep-seas-wiki/deep-seas/air/oxygen-diffuser.md) and give the diffuser a redstone signal.

As long as the diffuser has oxygen, the sealed rooms are full of breathable air. See [Oxygen](/create-deep-seas-wiki/deep-seas/mechanics/oxygen.md) for how much it uses.

## 4. Propulsion

[Submarine Propellers](/create-deep-seas-wiki/deep-seas/propulsion/submarine-propeller.md) push hard underwater and do nothing in the air. Four of them in a 2x2 square merge into one big propeller. [Water Thrusters](/create-deep-seas-wiki/deep-seas/propulsion/water-thruster.md) are the other option, fed with pumped water.

## 5. Assemble and dive

Turn the build into a ship with Aeronautics' Physics Assembler, like any other Aeronautics ship. Then fill the ballast and go down.

Keep an eye on the [Pressure Barometer](/create-deep-seas-wiki/deep-seas/instruments/pressure-barometer.md) or the Onboard Computer: they show how deep the hull can go. Past that limit the hull starts to crack, and once the submarine is 120 m deep or more, a block that gives way implodes the whole submarine. Shallower than that, the room just floods. Read [Cracks, breaches and implosion](/create-deep-seas-wiki/deep-seas/mechanics/cracks-and-implosion.md) before your first deep dive.