After climbing to about 1,500 feet and 30 minutes of uneventful flight, the pilot noticed an increase in engine coolant temperature. Shortly thereafter, water sprayed over the windscreen and the engine started to lose power. At that time, the pilot suspected a radiator water hose failed. He started a decent and landed the airplane in a field. During the rollout, the airplane struck several small pine trees and high vegetation resulting in substantial damage to the wings. During and examination of the airplane after the accident, an FAA inspector and the pilot discovered that the water hose fitting going into the radiator was fractured, and that the hose clamp and hose were still attached to the broken fitting. The reason for the failure of the fitting could not be determined.