Download Mineways to load your Minecraft map and transform into a .obj 3D Model , then go to Online Voxelizer there load your map .obj to transform into a voxel model .kvx then put your .kvx model into a basemap that you can create following this tutorial Create a Map OpenSpades Tutorial
Keep in mind that the maximum height of a map is 64 voxels.
Just to note, I am in active convo with the voxeliser guy, we may get it fixed
If you want to convert several maps for babel here are some tips:
For babel a rectangle 300 blocks long will be enough.
However, you can even use smaller areas if they are successful and reflect them several times, for example 4.
But you can also insert of course 512x512 areas, but pay attention to the game zone (300x150 (center)) it will be in the center of events.
You can also, for example, convert 1000x1000 islands to 500x500 if such an area is suitable
Water.vxl (2 MB)
Here is the water file: when you insert it the frames automatically set the correct map size. And then you can click import>colormap and import any water texture in bmp format, it is better to use a resolution greater than 512 by 512