RedactedNarrative: Vessel 1 was traveling downstream when it struck a large underwater object with its lower unit disabling the outboard motor. Vessel 1 began to take on water due to transom damage caused by the outboard motor impacting the unknown underwater object. Vessel 1 swamped and then capsized. Both occupants put on their pfd's and swam to the south shore. The vessel partially submerged, continued to drift southeast downstream to lock 14. The vessel was later towed back upstream to west mayo boat ramp where the owner tied it to the shore until it could be removed at a later time.