ArcGIS Pro 3.4 introduces the ability to add water area as inputs for flood simulation. However, this can only be done by digitizing the water areas. It would be better if we can import water area polygons such as rivers, which would provide more accurate vertices and also reduce time required to manually digitizing many many water areas.
Notice how the river polygon is digitized with few vertices which is inaccurate. Digitizing rivers in a 3D scene is very time consuming, especially when river feature classes are readily available for use as open data.