RedactedNarrative: Operator stated he and his passenger unloaded V1 with intentions on going to their cabin to remove some items from the rising flood waters. They launched V1 along side Hwy 63 and began easing down the ditch.  While motoring down, they caught a cross current that was going through a culvert that ran under Hwy 63. V1 struck the culvert and the current trapped V1 up against it; water quickly filled V1 causing it to sink. Both the operator and passenger were able to escape unharmed and get on dry land.  Damage to V1 included a dent/scrapes on the port side and the motor remained submerged for several days until retrieval was possible.