original: However, there are many compounds that are essentially, if not completely, insoluble in water.
simplifications: There are many compounds that don't dissolve in water. There are many ingredients that that can't dissolve in water. Many things do not dissolve in water. However, many compounds are practically, if not completely, insoluble in water. However,  many compounds cannot dissolve in water. Many mixtures will not break apart in water. There are many compounds that do not dissolve in water. There are many compounds that are basically insoluble in water. Many compounds are insoluble in water. There are many blend, though, which are merely, if not totally, put  in water.