As of the latest updates, Esri typically maintains Arc Hydro tools for only the last two ArcGIS Pro releases. For ArcMap versions like 10.7, these are considered to be in a "mature" state. This means:
Most of the tools are accessible via the Arc Hydro toolbar, where they are organized into six menus and nine tools. Additional tools have been developed within the geoprocessing environment and are available in the Arc Hydro toolbox for use in both ArcMap and ArcCatalog.