Instant Drown is a mod that causes you to drown instantly when running out of air.
It is meant to be used in hardcore modpacks or modpacks, that try to make Minecraft more realistic.
There are some mods that do similar things (e.g. Drowning Overhaul for 1.6.4-1.7.10), but none of them are available for 1.12 and above.
If you just want to higher the damage value you can disable instant drowning in the config and set the damage amount to any value you like.
