AirWater

It does the following
-Allows you to walk underwater.
-You don't drown.
-Even lava works underwater.
-You still cannot use flint and steel underwater tho.
-As you can see on the project picure, enderman don't teleport out of the water nor do they take damage.
Even tho it's made for 1.21.10, it works in 1.21.11.
Older versions are not tested but maybe work.