In Belize you don't qualify for a drivers license until you are 18 years old. You must be a licensed driver even to drive a golf cart on the public roads. Remember there golf carts are operating around heavy duty dump trucks, a few speeding pick ups, there are dogs and kids darting out all over the place and it is the law.
Of course if a young adult has a valid driver's license from another country the license will be accepted here.
There is an age limit for driving water craft too - I think it might be 18 also. It many not be "fair" but it would be wise to comply.