RedactedNarrative: Vessel #1 was anchored in pond.  Vessel #2 was rafted to vessel #1.  Owners got into their tenders and went off to have lunch at a vessel anchored in Vineyard Haven.  About 20 minutes later they saw a cloud of black smoke in the direction our their vessels.  No explosion was heard. They went right back and found both vessels engulfed in flames.  It was not determined which vessel started the fire or what the cause of the fire was.