I've had a similar situation happen, however I know what I had on. While fishing a shoreline, we noticed a few extraordinarily large carp (20lb +) tailing close to the bank. For some odd reason I had the feeling that i was going to be able to get one of them to bit a small crankbait. Throw it out beside them, and BANG! The biggest one takes it with full force. This huge sucker was peeling line off my reel like nothing! He turned and headed toward the boat. I reeled as fast as I could to keep tension on the line. Finally he went straight under the boat and kept on going, peeling drag just the same. he never did Turn again, and the hook pulled out of his mouth. Stronger line and a bit heaver of a reel, i have no doubt that he would have pulled the boat.