On a recent trip to the Panhandle of Florida, on the Apalachacola river, just down river from the famous Alum Bluff area, we found this 1" diameter, by 18+ " long tube with an outside shell, the inside filled with sand now...our segment is about 6" long. It broke apart as we were attempting to forage it . Does anyone know what creature made or lived in it. I have included three photos, you can see the somewhat segmented outer shell, and almost a double layer of shell on the end view. Thanks. We