Locations

I live near where the Florida scenes were shot.

The Dinsmoor mansion is part of the Ringling Museum in Sarasota and you can tour it. Cà d'Zan is what John Ringling named the place and it was his home. They made it look overgrown and rundown for the film, but it actually is as well kept as any historical home. Also, unlike in the film, it is furnished.

Joe's house is in Cortez, about 30 minutes away in Manatee County. It is still a fishing village and the movie provides an accurate portrayal.

I saw in the 'Locations' that they used Captiva island. I guess this was for the beach and ocean scenes, but I didn't spot that till I read it on here. Captiva is in Lee County and to get there from Cà d'Zan would be an hours drive south to Fort Myers, and then another hour over the Sanibel Causeway and on to Captiva.

I guess Captiva looks more rustic than the beaches in Sarasota, which are beautiful. The movie refers to "the Gulf" and kind of tries to portray itself as taking place in the panhandle or somewhere. Then later the movie pivots and makes Dinsmoor the richest woman in Florida and Estella going to parties "on Ocean." (alluding to Miami Beach's Ocean Drive, or something...)

All the scenes in Cortez and at Cà d'Zan are looking out over Sarasota Bay. The final scene with Finn and Estella, looking out over the water, you clearly see land across from where they are. That is Longboat key and if you look closely you can see several buildings that are highrise condos there.
At least there will be plenty implied.