Grass growing under water.

I was playing on a map and I found a village and I decided to customize it (like building new houses) and in the village there was a small amount of water I decided to make a small pond putting fish, seaweed and sea cucumbers but I realized that over time I started to grow even with seaweed or sea cucumber on top of the block.

I was placing blocks of dirt without grass but it grew naturally.

In the photos I noticed that the grass grows mainly in the blocks with coral, seaweed, among others.