Stones, Mud and More Water
I used the stone floor of the water tile and transformed it into an actual stone tile. I also created a completely new tile with only dirt. I then removed some of the stones from the stone tile and made a transition tile between the aforementioned two. To make it all a bit more lively I also made variants with a couple strands of grass.
Since I now had a dirt tile I used it to create an alternate water tile too.