I am coming south from Ontario Canada with no ADS-B out and am familiar with the the rules. My final leg will be direct KDBN to KMTH probably at 8500’ hopefully. One of the requirements is when over the Gulf of Mexico, above 3000’, and within 12 nm of shore you need ADS-B out. So when I break free of the tip of Florida I will be overflying “Florida Bay” getting to marathon in a decent but higher than 3000’ for some of that. Is “Florida Bay” considered the Gulf of Mexico?