Three Underwater Challenges

Breathing: Water Breathing potion, Turtle Shell, Conduit (infinite range effect). Water flow: sponge absorption (fastest) or sand/gravel fill (cheapest). Visibility: Night Vision potion.

Drainage Methods

Method 1: fill entire space with sand/gravel, then mine out from inside (air remains). Method 2: partition 5x5 cells, one sponge per cell center. Method 3: door trick (door creates air blocks) — best for 3x3 or smaller.

Warning: For 3x3 or smaller spaces, the Door Technique is simplest: place a door, it creates air blocks.

Glass Dome Construction

1) Build hemisphere template with dirt/sand. 2) Place glass against template exterior. 3) Remove interior dirt. 4) Sponge-drain interior. Recommended 12-15 block diameter (living+bedroom+enchanting). Large domes: multiple smaller domes connected by glass tunnels.

Interior Design

Aim for 'underwater palace': prismarine floor, quartz walls, sea lantern 'skylights'. Center: activate conduit. Window frames: trapdoors+fences. Entrance: water elevator (soul sand bubble column) from seabed to surface dock.