RedactedNarrative: OPERATOR ADVISED AFTER HE LAUNCHED V1 HE ATTEMPTED TO THROTTLE UP BUT THE BOW OF V1 WENT UNDER WATER AND ALMOST IMMEDIATELY FILLED V1 WITH WATER CAUSING IT TO SINK.  THE OPERATOR AND OCCUPANTS WERE ABLE TO MAKE IT SAFELY TO THE BANK. THE OPERATOR MADE SEVERAL ATTEMPTS TO TRY AND LOCATE V1 BUT HAS BEEN UNSUCCESSFUL.  HE FAILED TO IMMEDIATELY REPORT THE ACCIDENT AND DID NOT DO SO UNTIL A WEEK LATER; THEREFORE MUCH OF THE INFORMATION ON THE PASSENGERS IS UNKNOWN.