RedactedNarrative: On July 4,2016 two people were on a pontoon boat on Cherokee Lake in Jefferson County.  A line of strong thunderstorms moved through the area starting about 19:45.  Two people were caught in the storms.  Between storms operator tried to return to Cherokee Dam area.  He stated that due to the waves and wind he could only go about 5mph.  The vessel flipped and both subjects were under the vessel and were able to swim out from under the vessel.  Damage was due to vessel being submerged for approximately 5 hours and righting the vessel.