Grass can grow underwater

The problem
Grass can grow underwater and it doesn't update back to dirt.
What I expected to happen
That grass won't grow underwater and it will revert back to dirt
How to reproduce
Go to a normal flatworld and trow down a bucket of water and you will see that none of the flooded grass will turn into dirt.
Other info
I don't know if this has already been posted but i couldn't find 1. I am using optifine but I don't see how that would affect this.