How to Build a Modern Underwater Secret Base
Construct a sleek, hidden aquatic facility beneath the ocean floor featuring a bubble-column airlock, glass panoramic domes, and modern white concrete architecture.
- Read the tools, materials, safety notes, and steps below for free.
- Tap Start Camera Coach when you want hands-free voice help.
- Allow camera and microphone. Point your phone at the work; the coach watches your progress and tells you the next step.
🧰 Required Tools & Equipment
- ✓ Diamond or Netherite Pickaxe (Efficiency V)
- ✓ Diamond Shovel
- ✓ Furnace (for drying sponges)
- ✓ Water and Empty Buckets
- ✓ Night Vision Potions (8:00)
- ✓ Respiration III and Aqua Affinity Helmet
📦 Materials & Supplies
- ✓ Sponges (20-32)
- ✓ White Concrete (6-8 stacks)
- ✓ Cyan Stained Glass (4 stacks)
- ✓ Sea Lanterns (1-2 stacks)
- ✓ Soul Sand and Magma Block (1 each)
- ✓ Smooth Quartz Blocks (2 stacks)
- ✓ Dark Oak Trapdoors and Signs (1 stack)
⚠️ Safety Checkpoints & Warnings
- • Equip an Aqua Affinity/Respiration III helmet and keep two 8-minute Water Breathing potions on your hotbar during deep-sea excavation.
- • Set down a wooden door on the ocean floor immediately upon arrival to serve as an instant, infinite emergency air pocket.
- • Maintain line-of-sight awareness against Drowned wielding Tridents before establishing full perimeter enclosures.
📋 Step-by-Step Guide (6 Steps)
Survey the Seafloor and Secure an Airway Base
Scout a deep ocean trench or reef at least 20 blocks below the surface to ensure the base remains unseen from sea level. Place a wooden door or two stacked fence gates on the seabed floor to create an immediate air pocket and base camp. Clear hostile aquatic mobs around a 20x20 block radius and mark your coordinates.
- • A freestanding door on the ocean floor providing a stable pocket of breathable air
- • A flat, well-lit 20x20 seafloor perimeter free of hostile Drowned
- • Attempting to work on the seabed without an air pocket, risking rapid drowning during build setup
- • Building in shallow water where glass roofs render visibly from passing boats
Construct the Hidden Bubble-Column Airlock
Dig a vertical 1x1 shaft 12 blocks down into the seabed floor for your concealed entrance. Place a Soul Sand block at the bottom and fill every shaft block above it with water source blocks to establish an upward bubble column, or a Magma Block for downward descent. Place two wall signs or open trapdoors at the lower exit inside your base to hold back the water while allowing free player passage.
- • Particles rising rapidly up the 1x1 water shaft
- • Water suspended securely above the entry tunnel without flooding the dry chamber below
- • Using flowing water rather than full source blocks, which prevents bubble columns from activating
- • Forgetting barrier signs at the bottom, causing the water to flood the excavation tunnel
Excavate the Primary Living Chamber
Dig out a 15x15 block subterranean room with a 5-block ceiling clearance extending out from your airlock exit. Use an Efficiency-enchanted pickaxe and shovel to clear stone and dirt quickly. Square off all corners and replace outer perimeter walls with smooth stone temporarily to map room boundaries.
- • A completely hollowed, dry 15x15x5 subterranean space beneath the ocean floor
- • Evenly squared perimeter walls ready for decorative block replacement
- • Digging ceiling blocks upward into gravel patches that trigger suffocating cave-ins
- • Misaligning room dimensions, making subsequent glass dome integration uneven
Frame and Seal the Panoramic Glass Dome
Carve an 11x11 circle into the chamber ceiling breaking through into the ocean water. Build concentric rings of Cyan Stained Glass rising 3 blocks upward into the open sea to create a watertight hemispherical dome. Seal the apex block with glass to complete the exterior shell before beginning drainage.
- • A fully sealed glass dome protruding into the ocean overhead with no gaps letting in flowing water
- • An unbroken exterior glass contour visible from the ocean floor
- • Leaving single-block gaps along corner glass diagonals, allowing continuous flooding
- • Accidentally placing solid opaque blocks that ruin the modern glass aesthetic
Evaporate Trapped Water with Wet Sponge Cycling
Divide the flooded dome chamber into 4-block wide lanes using temporary dirt or sand walls. Place dry sponges in the center of each water section to immediately clear out all water sources within a 5-block radius. Collect the wet sponges, smelt them dry in your furnace using coal or lava buckets, and repeat until the interior is fully dry.
- • Zero water blocks remaining under the glass dome or inside the main chamber
- • Temporary dirt divider grids completely removed without exposing remaining water pockets
- • Placing sponges in large open water without dividers, causing infinite ocean water to instantly refill the space
- • Breaking wet sponges with a pickaxe rather than bare hands or a hoe, causing unnecessary tool durability loss
Install Modern White Concrete and Flush Lighting
Replace all temporary dirt and stone walls with White Concrete for clean, minimalist lines. Frame the floor using Smooth Quartz blocks with Sea Lanterns countersunk into the perimeter edges, covered by light gray stained glass or white carpets for seamless flush illumination. Detail the panoramic dome border with Dark Oak Trapdoors to provide crisp, high-contrast framing.
- • Smooth, unbroken white concrete walls and quartz borders throughout the entire room
- • Sea Lanterns hidden flush under glass or carpet providing spawn-proof light level 9+ everywhere
- • Using standard torches on modern builds, which clashes with the sleek high-tech aesthetic
- • Leaving light levels below 8 in floor corners, allowing mob spawns inside your completed base
Credit: inspired by an original tutorial by Milo and Chip — watch the original on YouTube.
Don’t have everything?
- No Sponges? Sand or gravel gravity-clearing grids
- No Sea Lanterns? Glowstone, Shroomlights, or Froglights hidden under white carpet
- No White Concrete? Smooth Quartz blocks or White Terracotta