I have been trying to figure out how to make a flood delineation map, and the tool runs, but I'm getting this error "001003: Datum conflict between input and output." I thought this would be as simple as the spatial reference system datum, but I have them all in the same reference type. I thought the datum error might also be from the water datum measurement compared to the raster elevation measurement, but even changing the point water level height did not fix my problem. I'm not sure what the problem would be at this point.
The documentation says that this is just a warning that can be ignored (https://pro.arcgis.com/en/pro-app/tool-reference/tool-errors-and-warnings/001001-010000/tool-errors-and-warnings-01001-01025-001003.htm). But if you wanted to resolve this, you need to check the environment settings (https://pro.arcgis.com/en/pro-app/tool-reference/environment-settings/output-coordinate-system.htm). A 2nd measure would be to check that the map/data frame is also in the same datum.
I do not understand what you mean by the "water datum measurement" and "changing the point water level height".