While under survey on what may become my new boat, we found what looked like a puddle of diesel oil under the fuel tank. This tank is located under the rear stateroom berth. We could not find a source for the fluid, and all of the fittings seem tight. There did seem to be some sweat on the tank, and the fluid did look like there was water mixed with it. Does anyone have any ideas as to what may have caused this? The boat was on the hard for the last year, and the staining indicated that this fluid had been there for some time, so it was not a result of a pretrial refuel. Any ideas or experience in this area would be appreciated. Thanks, Larry K