Drowned don't attack when in 1 block deep water

Ok so i was doing stuff in my suvival world and i saw a drowned, so i killed it for the exp and maybe a gold ingot. I noticed it wasnt attacking me. 

Steps to reproduce:

1. Make a new flat world.
2. Type this command: /fill 0 3 0 10 3 10 water
3. Type this command: /summon drowned 5 3 5
4. Type this command: /gamemode 0
5. Go to {X:5 Y:3 Z:5}. 
6. The drowned does not attack you. ❌