Overheating

I was run off the road and my car bottomed out hard on an embankment as a result. The temperature gauge briefly flipped to hot at the moment of impact and then back to a normal temperature. I drove about a mile home, and the car seemed okay. I could not see any visible leaks. I went to drive it the next day and within a mile or two it overheated. I was next to a shop and pulled in. They said there was water in the oil and that they said they do not handle this type of thing there, so I left the car parked. There is water in my oil. Could the impact with the embankment have caused this damage? And what do you think the damage is and what caused it? And what do you think is the problem and what can I do to fix it?