How do I patch an underground spring coming under the house from underground footer?

At my mother's house, there is an underground spring making a 4ft sink hole under the house and a mini creek under there as well. it's entering through an apparent hole in the foundation footing underground. I'm told I have to dig down there from the outside and patch it somehow. What would be the best way to patch it once I dig it up on the outside (maybe 6ft underground). Is it possible to dig it up only at the spot where the water is entering, or would i have to dig up the entire perimeter to patch/seal it all? Any advice? Thanks in advance