While we wait for the water and physics, you can land the float planes at Dry Tortugas if you know the secret landing area. This only area that will work for now is directly underneath the airplane and around the new dock. Everywhere else is a protected area for the manatees, for now.
Here is a better layout for the water landing area for Dry Tortugas. I have a fsCP airport here but the elevations. static aircraft, wind turbines and private dock have to be added to the file. PM me and I will send you the necessary upgrades and changes needed to make it functional.