Waterlogged caves become floating water tunnels when they intersect with open-air caves/ravines.
What I expected to happen was...:
The ravine/cave to become waterlogged.
What actually happened was...:
A strange bug causing strange but interesting floating water tunnels.
Steps to Reproduce:
1. Find a world where a waterlogged cave intersects with a ravine or cave, e.g. -8392751900383477890
2. Look around, e.g. -629 27 78
3. Contemplate life.