I believe that there are boat ramps that must accommodate very large variations in lake water levels. When the lake is at its peak height, the boat ramp may appear to be very short. However, under the water, the ramp continues at the same slope for whatever length is needed to make the ramp usable when the lake level is low.
The momentum of the vehicle will carry it quite far whether it floats out into the lake or rolls on the ramp underwater.
Even taking all of that into account, the distance and depth seem a bit extreme to me. Unless the driver was totally inattentive, she should have realized that she had hit water and been able to stop on the ramp before she got too far into the water to escape. Definitely a strange set of circumstances.
This lake is called the Atlantic ocean