The pilot reported that during the business flight he landed in a pasture. The grassy field looked adequate for takeoff. The pilot stated to the National Transportation Safety Board investigator that he did not observe a fence located at the distant end of the pasture. The airplane became airborne, and when it was about 6 feet in the air, the tail snagged a wire fence. Thereafter, the airplane descended into the ground. As the airplane decelerated it nosed over and came to rest partially submerged in water. The pilot reported that he had not experienced any mechanical malfunction with his airplane.