It happens with naturally generated as well as placed blocks, and is purely a visual bug where the water is invisible and in the case of seagrass you see a 2D version of the seagrass texture on the top side of the block. You can swim through these blocks as normal, and once you break the seagrass the water renders normally again.
It happens with naturally generated as well as placed blocks, and is purely a visual bug where the water is invisible and in the case of seagrass you see a 2D version of the seagrass texture on the top side of the block. You can swim through these blocks as normal, and once you break the seagrass the water renders normally again.