RedactedNarrative: V1 was traveling in the Lower Vallier ditch of Bayou Meto WMA when it slowed to check on a docked vessel at the water control structure.  V1's engine quit and V1 was overtaken by the extremely swift water flowing through the control structure.  V1 struck the water control structure and capsized; ejecting both occupants.  V1 sustained hull damage from bow to stern.