RedactedNarrative: Vessel was just outside of the no wake zone at cookeville dock on center hill lake.  The vessel was stopped at the time of the incident.  Subject was on the back swim deck of the vessel, when she attempted to step into a tube in the water.  As she done this, she slipped and fell backwards.  She hit her head on the vessel''s swim platform.  She was experiencing numbness in her fingertips.  The paramedics deemed it necessary to air lift her to skyline medical in nashville, tn.  She had some test/ scans run.  They released her with a concussion and minor head contusions.