Gather soul sand
Gather magma block
Gather water buckets
Gather glass or any building blocks
Build a vertical shaft
Place blocks around the shaft to form a column
Leave the inside hollow
Place a door, sign, or trapdoor at the bottom if needed to hold water
Fill the entire shaft with water source blocks
Place soul sand at the bottom to make an upward bubble elevator
Place magma block at the bottom to make a downward bubble elevator
Use kelp to convert flowing water into source blocks if needed
Enter the water column to move up or down
Add a roof or top exit if desired