Florida
Agencies - Roughly speaking this are north to south
https://www.plumleegulfbeachrealty.com/ - Indian Shores et. al.
http://www.ourcondo.com/ - Indian Shores
https://www.vacationrentalpros.com/ - Venice to Fort Myers Beach, includes a good number of dog houses.
http://www.peninsularhouse.com/ - Covers many parts of Florida
http://univacus.com/ - Fort Myers to Naples
https://www.royalshellrentals.com/ - Estero to Naples
http://www.marcovacation.com/ - Marco Island and Naples
http://www.whitesandgetaways.com/ - Marco Island
http://www.iescapeaway.com/ - Marco Island
Beachfront Condos - North to South
Somerset - Marco Island, expensive