RedactedNarrative: On 08/08/15 vessel 1 (V1) was launched at Gavin's Point Boat Ramp on Lewis and Clark Lake in Yankton County, South Dakota with one operator (O1) onboard. O1 operated V1 at idle speed through the marked navigation channel south onto Lewis and Clark Lake. After passing the last navigation buoy O1 turned V1 in an eastern direction. O1 began motoring V1 onto plane. V1's transom, engine and lower unit dropped deeper in the water column as O1 placed V1 under power. 
  
  V1's lower unit impacted a hard submerged object, evident by sound and bow drop. V1 traveled at approximately 5-10 miles per hour at the time of impact. O1 placed V1 in neutral immediately after impact. O1 lifted V1's engine and lower unit out of the water, revealing extensive lower unit damage. O1 observed fluid leaking out of V1's lower unit.
  
  O1 returned to Gavin's Point Boat Ramp with V1.
  
  WCO surveyed accident location using sonar and was unable to locate any definitive objects sticking out of the substrate.