was there any metal in the oil as you drained it? have you removed the oil filter and inspected it for metal peices?
2 things could make water get in your oil, a busted head gasket, or a bad water pump seal, if enough coolant gets in the oil, you will lock the engine, which is what it sounds like happened. hopefully didnt rip anything apart (there would be metal all over the bottom of the engine)
the other possiblity is that you blew it up, and it shredded everything in the engine and busted the water jackets in the engine and basically just destroyed everything. it doesnt sound like thats what happened.