If it were me, I'd make sure the hole is large enough for you to get a good wad in there. If yr mixing yrself, only use enough water to make it workable. Plug the hole with the wad and it should set/expand to be water tight.
If you find the rest of the patch starts failing, then be prepared to chip out the whole patch and reset it. But I bet the patch will work fine. That stuff expands hard and tight.