Next step is to design your own Mapbox Style on Mapbox Studio by using mbtile which was produced before.
For better designs of beautiful water maps, you might need to design your own icons for your layers. You may use the following icons for your reference.
Narok Water and Sewerage Services Co., Ltd, KENYA : narwassco/water-iconsWater and Sanitation Corporation, Ltd, RWANDA : WASAC/water-iconsNakuru Water and Sanitation Services Co., Ltd, KENYA : nakuruwater/water-iconsYou may need to create an account of Mapbox Studio. Also, please keep your public accessToken as well.
You can see official manual of Mapbox Studio here.
You may need to repeat process of genrating mbtiles and styling in Mapbox Studio for finalying your stylefiles.
However, Mapbox Studio has limitation to use third party vector tiles sources. So you can also use Maputnik Editor for this purpose.
Once you created your Mapbox Style, it is easier to use Maputnik Editor to modify your style. It is free to use online. You can use any third party vector tiles sources.