Have a problem with flying grass in lakes (plains)

What I expected to happen was...:

Normally, the lakes of plains biome are not with grass flying on...

What actually happened was...:

I walked in plains biome and I found many lakes with flying grass (tallgrass) on top of it...

Steps to Reproduce:
1. Find a plains biome
2. Find a little lake
3. Don't fall in, just see the grass...

I joined a screenshot