The Bug:

Air pockets can be created underwater when sand or gravel is updated.

Here is an example:

Seed: 6839161054487471859
Coordinates: /execute in minecraft:overworld run tp @s 8232.08 53.46 -1033.92 1338.94 10.80

Steps to Reproduce:

1. Generate a world with the seed provided above and teleport to the given coordinates.
2. Destroy the sand block that you're looking at after running the teleportation command and wait for all nearby blocks to be updated.
3. Take note as to whether or not air pockets can be created underwater when sand or gravel is updated.

Observed Behavior:

Air pockets can be created underwater when sand or gravel is updated.

Expected Behavior:

Air pockets would not be able to be created underwater when sand or gravel is updated.