How to Build an Underwater Starter Base in Minecraft
Construct a functional glass-domed underwater starter base in Minecraft Survival mode, including air pockets, water displacement, and airlocks.
This guide shows how to build an underwater starter base in minecraft in 20-30 minutes. Start with establish an ocean floor air pocket; follow the safety notes and step checkpoints below.
Visual step map
See the full sequence before you start, then check off each step as you go.
0 of 6 steps checked
Materials and cost planner
Select the items you plan to buy, adjust any estimated price, and calculate the selected total.
Editable rough U.S. retail estimates. Estimated all listed: $170.00. Prices are planning estimates, not quotes — tax, store, brand, size and quantity will change them.
Time and finish planner
Estimate active working time from the number of steps in this guide.
File transfer time calculator
Estimate how long a download, upload or local transfer should take at a given connection speed.
Real transfer time is usually longer because of overhead, server limits, Wi-Fi conditions or other network traffic.
- Read the tools, materials, safety notes, and steps below for free.
- Tap See 20-second demo if you want to understand it first.
- Tap Start Camera Coach when you want hands-free help, or Voice-only if you do not want to use the camera.
- Allow camera and microphone. Point your phone at the work; the coach watches your progress and tells you the next step.
🧰 Required Tools & Equipment
- ✓ Iron Shovel
- ✓ Iron Pickaxe
- ✓ Water Bucket
- ✓ Oak Door (for air pockets)
- ✓ Torches or Lanterns
📦 Materials & Supplies
- ✓ 64x Glass blocks
- ✓ 64x Oak Wood Planks
- ✓ 64x Sand or Gravel blocks (for water clearing)
- ✓ 2x Oak Trapdoors
- ✓ 1x Bed, Crafting Table, and Chest
⚠️ Safety Checkpoints & Warnings
- • Keep oxygen bubbles monitored at all times; replenish air before the last bubble pops.
- • Place a wooden door underwater immediately to create a permanent air pocket for breathing.
- • Maintain full hunger bars to ensure rapid health regeneration if drowning damage occurs.
📋 Step-by-Step Guide (6 Steps)
Establish an Ocean Floor Air Pocket
Dive down to a flat ocean floor area with at least 5-8 blocks of water depth above it. Place a solid block on the seabed, then place a wooden door directly on top of it and open it. Stand inside the door frame to instantly refill your oxygen bar safely.
- • A wooden door stands open on the seabed surrounded by water.
- • Player stands inside the door frame with full oxygen bubbles visible on HUD.
- • Placing the door on sand without clearing loose terrain, causing it to pop off.
- • Letting oxygen drop below two bubbles before placing the breathing station.
Lay the Base Foundation Ring
Clear a 7x7 flat square on the seabed using your shovel. Lay down an outer border of Oak Planks in a 7x7 circle layout (corners cut diagonally: 3 blocks along each edge). Fill the interior floor with Oak Planks so you have a solid platform.
- • A flat 7x7 rounded-corner wooden ring rests evenly on the ocean floor.
- • Solid wooden floor installed with no gravel or kelp inside the perimeter.
- • Making the foundation asymmetrical, throwing off the dome geometry.
- • Leaving kelp or seagrass beneath the floor blocks.
Build the Glass Dome Walls
Place glass blocks along the outer edge of your wooden ring, building up 3 blocks high. Step inward on the 4th layer and cap off the roof with a 3x3 flat square of glass on top to form a curved observation dome.
- • A complete, enclosed glass dome structure visible underwater.
- • No gaps or missing glass blocks along the seams.
- • Accidentally breaking glass without Silk Touch, permanently losing the resource.
- • Leaving a single block gap in the roof, which prevents water clearing later.
Displace Interior Water with Gravity Blocks
Create a top hatch entrance by breaking one glass roof block and placing a trapdoor. Drop inside and completely fill every interior air/water block with sand or gravel from the ceiling down to the floor, eliminating all water source blocks.
- • Interior of the glass dome is completely packed solid with sand or gravel.
- • No water texture visible through the outer glass walls.
- • Leaving single water pockets untouched in corners, which will cause water to flood back in.
- • Filling from the bottom up instead of dropping blocks from the top down.
Excavate Sand to Reveal the Dry Interior
Enter the dome and dig out all the sand or gravel using your iron shovel. Start from the top layer and work downward. Once cleared, verify that the interior remains 100% dry and free of floating water sources.
- • Hollow, fully dry interior room enclosed by glass.
- • Torches can be placed directly on the walls and floor without washing away.
- • Breaking an exterior glass block with the shovel by accident, re-flooding the room.
Install Airlock and Starter Furnishings
Install a double-trapdoor or double-door airlock at your chosen entrance to stop ocean water from flooding in. Place a bed against the wall, a crafting table, double chest, furnace, and wall lanterns to complete your safe underwater starter base.
- • Functioning airlock entrance allowing entry without water ingress.
- • Fully illuminated room containing a bed, crafting table, chest, and furnace.
- • Opening outer doors while inner doors are open, letting water spill onto workstations.
- • Inadequate lighting, allowing hostile mobs to spawn inside your base at night.
Credit: inspired by an original tutorial by Milo and Chip — watch the original on YouTube.
Don’t have everything?
- No Sand or Gravel? Dry Sponges (if obtained from Ocean Monument)
- No Oak Door? Two stacked Sugar Cane or a Fence Gate placed on the sea floor