Mobs take drowning damage too quickly

Whenever a mob begins to drown, the damage immunity gained is the same value for standard damage types (which is .5 seconds), making it so that mobs drown at twice the speed that players do (which is 1 second).

Steps to Reproduce

1. Build an encased 3x3 box

2. Fill it with water

3. Spawn any mob in that box (suggesting a fox here because of higher health yet smaller size: MCPE-48233)

If done correctly, when this mob begins to drown, they will take damage every half of a second, the same immunity timer given for projectile and melee damage.

Video Examples

https://youtu.be/nyDD5-QZuyE
https://youtu.be/c_cd6tbBHjQ