No, not wearing the seat belt is not safer because safety belts prevent injury during impact, and thus increase your chances of remaining conscious and being able to escape your vehicle in case of danger. Cases of fire or water submersion are extremely rare, and safety belts are still the best way to ensure you are not severely hurt before the fire or submersion occur.
Statistics show that a fire or water submersion following a crash is extremely rare. When they do occur, the greatest danger is the actual impact that precedes the fire or the sinking in the water. Safety belts prevent injury during impact and can keep you conscious so that you can escape your vehicle.
Properly worn safety belts seldom cause injuries. A safety belt may cause superficial bruises, but studies have consistently shown that these are generally much less severe than would have been the case without a belt. According to the NHTSA, in 2010, almost 50.4% of people killed in automobile accidents in Florida were not wearing a seat belt.
Also, the Florida safety belt law applies to any car, pickup truck, and van operated on Florida roads and manufactured after 1968, and states the following:
In 2017 a Miami High School was the winner of the national Seat Belt Save Challenge which was initiated by the NHTSA and NOYS to increase seat belt usage among young people.