Vast areas of tidewater were deemed to be in flood prone areas, even though they haven't flooded in the last (at least) 200 years.
Yep, that makes the insurance premiums go up, and I reckon that's to compensate for the Insurance Industry having to pay out for rebuilding homes that get the beach washed out from under them in storms, among other things.
If that home had been there 50 years, for instance, the cost of getting the necessary permits alone has increased astronomically, as have the number of hoops to jump through in order to get them, and with government policies affecting the cost of building materials and fuels, the cost of rebuilding is at least going to keep pace with inflation.
The actuaries are just trying to stay ahead of the game.