Flooded caves and trenches get cut off above sea level

The bug

In 1.13.2, underwater caves and flooded ravines could generate above the surface (without being filled with water), but this is no longer the case. This is also apparent in "cave" buffet worlds, with this glitch respecting the sea level in the buffet world.

Seed: -5613519190629551455
Coordinates: /execute in overworld run tp @p -2644 60 -1290