I've never been able to grow them long-term if they're completely submerged, although it does take several months for them to waste away. It also seems as though a plant that is growing partly out of the water will maintain its submerged leaves much longer than one which is completely submerged.
The several pics in this thread that "prove" the plant will grow completely submerged don't show the plant completely submerged, there seems to be an emersed portion in each case.
Years ago it was common to see several species of terrestrial plants...prayer plants (Maranta), various types of Draceana, ivies, etc...sold for aquarium use. That practice seemed to have finally disappeared. Now that the idea of using pothos and others for nitrate reduction is becoming commonplace, we're back to drowning terrestrial plants again.