DO NOT GO TO FLORIDA DMV.ORG. It is not a State of Florida site, and says so at the top. There is no telling what additional fees, paperwork, etc. you may encounter.
If you are registering for the first time, you MUST do it at a local office, according to this document:
https://www.flhsmv.gov/motor-vehicles-tags-titles/vessels/vessel-titling-registrations/
Look under "applying for vessel registration". Also check the section called "Applying for Title". (Note that not all vessels need to be titled.)
If you are already beyond this stage, and are just renewing your registration, use
www.gorenew.com.
What Benny wrote above about local tax collector's office employees was the opposite of my (in person) experience. The person looked at the title that was signed over to me and said, "yep, it qualifies, so I'll put it in the system so you get the correct rate". However, the statute clearly states that certain "certification" is to be submitted.
328.72 Classification; registration; fees and charges; surcharge; disposition of fees; fines; marine turtle stickers.—
(1) VESSEL REGISTRATION FEE.—
(a) Vessels that are required to be registered shall be classified for registration purposes according to the following schedule, and the registration certificate fee shall be in the following amounts:
(I have removed the rest of this paragraph, which lists fees. In the next paragraph, the boldface emphasis has been added by me.)
(2) ANTIQUE VESSEL REGISTRATION FEE.—
(a)
A vessel that is at least 30 years old, used only for recreational purposes, and powered by the vessel’s original-type power plant may be registered as an antique vessel.
When applying for registration as an antique vessel, the owner of such a vessel shall submit certification, as prescribed by the Department of Highway Safety and Motor Vehicles or from a marine surveyor
that the vessel meets the requirements of this paragraph.
Many owners I've talked to have said that the "certification" is more about "original-type powerplant" requirement than the age of the vessel, but who knows. As to the age of the vessel, if it has just turned 30, you may want to enter the vessel's HIN into an online decoder, and print out the output, which will establish the MONTH and year the boat was built. If it's 30 years and a day, then it meets the requirement in the statute.
If you encounter someone at the local office that cannot do math, ask for a supervisor. Go at a time not likely to be crowded, which eliminates Mondays and Fridays. Afternoons are often better than mornings. If you don't get what you think you should, and a supervisor cannot help, simply say "I'll come back another day", and go to another office.
By the way, the discounts for EPIRBs and PLBs ended on June 30, 2017.