A little confused by your question. Are you talking about home made sauerkraut? If you are fermenting in a mason jar, wait till the ferment is finished and then keep it in the fridge and at that point you don't have to worry about keeping it submerged. If you are still in the process of fermenting, yes, it always has to be submerged and you really shouldn't be fussing with it till it is done. And if you ever have to add more liquid to your sauerkraut for any reason, you would add brine- not pure water.