A third DUI conviction in Florida is classified as a third-degree felony, while a fourth or subsequent conviction is a second-degree felony. These convictions carry severe penalties, including up to 5 years in prison, fines up to $5,000, a license suspension for up to 10 years, mandatory IID installation for at least 2 years, vehicle impoundment for at least 90 days, probation for up to 5 years, and the requirement for SR-22 insurance for a minimum of 5 years.