That's a theory, but... In the case of Cape Coral, I'm guessing that's not really feasible. The area being surveilled, like in the other two cities/towns, is a small area, surrounded by water on three sides, an extensive canal system and (if I'm not mistaken) purely (or at least largely) residential. I'm under the impression that smart cities need to be self-contained with grocery stores, pharmacies, doctors, etc. Edit: there ARE businesses among the area being surveilled, just checked the flight pattern again. My memory (mistakenly) had the survey skimming closer to the coast, but, in fact, it diagonally scans from NW to SE. Still loads of canals there, mostly residential.

Another theory is they might be hunting for submersible drug-running operations as the Florida coast, in general, is an opportune destination for bringing contraband in. That would explain why, when the reporter for the Cape Coral scan (allegedly) tried checking with the authorities, they didn't provide any answers. If they are hunting drug-runners they're not going to advertise it.

Due to the fact that each of the three cities/towns mentioned that have had these survey flights buzzing overhead have a considerable canal system where the surveying is occurring, I'm leaning towards the ecosystem theory.

In today's world, though, doc, we absolutely can't rule out nefarious activity.