Building Underwater: A Comprehensive Guide to Aquatic Development

Building Underwater: A Comprehensive Guide to Aquatic Development

Disclaimer: Somewhat late the author of this article discovered that the subject of underwater construction had been dealt with by another forum member. Hopefully this edition (which is entirely original) will either clarify what has been discussed or provide alternate methods.

Why build underwater?

Players typically avoid using oceans and lakes as construction sites, and for good reason. Water is a messy, dangerous, and all-around uncomfortable environment to work in. So why try to build in it?

All the aforementioned negatives can be positives for you…if you take the right steps. Bodies of water are real estate, just like solid ground—only with much less competition due to the unpleasantness. Whether you’re on single player or multiplayer, the ocean will begin to seem much more tempting after every dry surface near spawn becomes jam-packed with buildings. For those who value secrecy and seclusion, deep water can also be a place of refuge.

It should also be noted that underwater builds have an intrepid flair. This effect cannot be paralleled in any other environment.

1. Choosing Your Location

Before you decide where you want to build, be sure you understand the nature of what you’re building. If it’s relatively small, a lake may provide all the space you need, but remember that most lakes are only around 20 blocks deep, so any construct with a greater height than that may not fit. Oceans can reach depths upwards of 100 blocks below sea level, making them much more versatile (though less navigable) than lakes.

A substantial difference in depth is seen between the two bodies of water.

Another thing to consider is how you will access your build. Needless to say, the closer it is to shore the more convenient it will be to travel to and from it. However, if secrecy is a concern, you may feel led to start construction further away from land. Some builds are accessed via an underground tunnel which descends into the earth and then opens out into deeper water. If this is how you want to reach your underwater creation, you may be forced to begin building it very close to the shore, or perhaps even directly attached to the ocean walls.

This build uses an underground tunnel as a means of entrance. It is easily discovered by following the downward path of the shore…

2. Taking the Plunge

You’ve chosen your location. Before you dive down, make sure that your inventory holds all of your immediate needs. Having a trade portal of your own will greatly reduce the number of items you have to take with you, but in any case, kelp, steel lanterns, food and a shovel are necessities. If you don’t have a trade portal, you may have to add to that list some of the following: a pickaxe, building blocks, doors, trapdoors, and buckets. For reasons explained in a later passage, it is also advisable to bring steam generators with you on your underwater foray.

The essential diving inventory. Items in tens indicate that they will be used in bulk.

While it is possible to swim without light, your movements are inhibited, and you are unable to spot irregularities in the surface such as caves and unnatural slopes. This cannot be helped if you begin your dive offshore, and if your build is a sizable distance from land, you may be forced to go without light as you descend. However, if your construction site is relatively close to the edge of the water, you can adhere to the shoreline as it slopes downward and place steel lanterns to guide your path. Your choice of these two methods will be based on whether you prefer a shorter swim or a safer swim.

It hardly needs mentioning that you will, out of necessity, be forced to eat kelp at regular intervals to replenish half of your oxygen bar. Additionally, in the incident of a shark attack, eat food immediately. The kelp will help you recover health, but by small increments, and until your health is full again your movement speed will be diminished, making you more vulnerable to another attack.

3. Preparing Your Work Area

The following instructions only apply if you intend to make immediate use of a trade portal. To place a trade portal, you must have a dry space at least three blocks tall. Dig an appropriately sized hole out of the ocean floor or ocean wall, and then seal it with a block. Use buckets to remove any water that may have entered.

A trade portal hole of minimum size.

Once you are through using your trade portal, remove the sealing block to exit the hole. The trade portal, although exposed to water, will remain. If you wish to have your trade portal on the surface rather than in a hole, build the space out of blocks atop the ocean floor.

To keep your work space as clear as possible, break off or dig out all the surrounding kelp. Even if you wish to have kelp near your finished build, it’s better to plant it later after the construction phase is complete.

The final method in this section outlines the use of the aforementioned steam generators. Not only is a steam generator a source of light, but the heat it produces has a healing effect. Since they can only be placed on a dry block with backwall, you can perform the “trade portal hole” process in miniature for each steam generator. As long as you have placed enough of them and you remain in close proximity to them, the damage you sustain from drowning will be quickly replenished. In this manner you will no longer be forced to regularly eat kelp, a practice which would interrupt your building process.

A ready work space.

Your blockhead can still feel the healing effects from a distance.

4. Beginning the Build

You may have noticed that when a block is removed underwater, it removes with it part of the natural ocean “backwall”, letting in daylight. While this can be helpful to some, others find the intrusion of unwanted light an annoyance. Also, if you’re building in a colder climate, the water around the removed backwall will freeze, creating an obstruction that is difficult to remove. To patch the hole in the backwall, you only need to place a block over it. The difficulty is in removing the block without reopening the hole. One method of achieving this is performed by placing an ice block directly above the cover block and mining the cover block before the ice melts. If you are able to do this successfully, the hole will be patched with no mess.
Since you’ll probably be removing many blocks during construction, the first thing you might want to build is a “canvas” for your model. This is simply a large section of backwall with solid blocks along the top row. Once the entire project is done you can remove this top row using the ice block method.

A glass construction canvas.

This utility prevents accidental openings in the ocean backwall. Additionally, any items dropped during construction will be caught by the top row of blocks before they float to the surface.

Now you can easily build the frame of your model. Be sure you know where the entrances are so that you’ll be able to place doors and trapdoors at the outset.

Once you’ve finished the frame, there are multiple methods of removing the water from its interior. One is to simply gather the water in buckets and empty it into the ocean, but this is slow and tedious work. A quicker method involves placing and removing doors, which don’t displace water. If you decide to use doors, lay down soft blocks like glass or sand at the base of your build so that the doors you set on it can be quickly removed.

Remove doors on a soft surface.

Other ways to eliminate water include surrounding the water with ice torches and mining it after it freezes. This is the most expensive course of action, and the time it saves is largely spent waiting for the ice to form. A final method is to fill your build with blocks, leaving no room for water. This is plausible with smaller builds, but is hardly viable in larger ones. A combination of all four methods is sometimes the ideal route.

Don’t remove the backwall canvas until your build is completely finished. It will allow you to easily make edits to your construct as you progress.

5. Finishing Touches

Now that the inside if your build is dry, you can replace the backwall from the canvas with the backwall of your choice. Then migrate your trade portal inside. You might also want to move the steam generators to your build’s interior to create a perimeter of healing effect around it.

Replaced, repainted backwall.

At this point the direction you take with your creation is entirely up to you. Take into consideration your options for lighting. Steel uplights, for instance, can be placed in water. When arranged on the uppermost blocks, they might function as a beacon to help you more easily locate your build.
Depending on how much time you plan to spend with your finished project, you might want to include necessities like a bed and food, including enough kelp to help you reach the surface when you decide to exit your aquatic refuge.
You can also restock your surroundings with kelp and fish if you so choose.

Now use the ice block method to remove the top row of your backwall canvas. If you suspended your build on the canvas without attaching it the ocean floor, clear the rest of the backwall under it with a tool. You’re finished! Consider yourself an ocean-dweller.

My minimalist rendition of the concept submersible, Manatee.

My hope in writing this guide was that it might inspire more players to bring their creativity underwater. If you’re one of those players, please use this thread to share pictures of your model, and even to detail your construction process! Your work may help others who want to tackle the depths.

If you have any edits or suggestions for improvement, by all means share them with me in the comments or in a private message.

Finally, if you found this guide helpful, please give it a like to let me know.


Wow, very creative and appreciated help.

This is awesome.

Nice topic/thread you’ve made.

I’m sure this’ll be useful for another time, so I’ll bookmark it. :slight_smile:

I’ll now be taking your useful tips…
To make an underwater house.

Nice thread! :smiley:


Nice guide… But how did you do the spoilers. Mine don’t do spaces

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@Zeekiel Thanks! Be sure and at least share a picture of your build here when it’s finished.

@Frater_Universe Good question. I put quotation marks around the summary.


Very helpful! Water is one of my favorite places to build, but it always ends up messy :sweat_smile: This is some useful information!


Great guide! Very comprehensive. I love the secrecy and unique style of underwater bases.
Your suggestion of a backwall “canvas” is very helpful. I’ve never thought to do that. Most of the underwater builds I’ve done have been small, hidden bases in relatively warm climates, not causing an issue with displacing a lot of water, or water freezing from air blocks. I’ll have to remember that if I’m planning to build a larger design beneath the waves!


Phenomenonel guide! I’ll use it when I build my underwater death shark for sure >:)


Sweeeeet guide!!! I love finding cool stuff underwater :grinning::grinning::grinning:

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This is a good guide, but do you have any suggestions when building suspended in the water? Like not on the ocean/sea floor, suspended 30 blocks above it for good camouflage? Thanks.

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Good question. The backwall canvas can help with that to a certain extent. You can place blocks higher on it and just remove the backwall that remains underneath. However, it’s impractical to set up a thirty-block tall canvas, so for that I would recommend you build a column of the necessary height, start your construct around the top block of the column, and then break all the blocks below it. Remember, as long as there’s something above a block, you can mine it underwater without opening up a hole in the natural ocean backwall.

I’ll try to revise some of my article to include advise on building underwater without proximity to a surface. Thanks for bringing this to my attention!

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Thanks, I’ve been trying to build a giant prison underwater where prisoners cannot escape easily when I remove the lights. The only escape would be the spawn portal.

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