Find out how they measured the distance. I would suggest having your property resurveyed and find the NAVD (NORTH AMERICAN VERTICAL DATA) or NGVD (NATIONAL GEOLOGICAL SURVEY VERTICAL DATA) ELEVATION of your property from the Mean High Water Mark. Not from the shoreline. If the NAVD or NGVD is at least 6 inches above Base Flood Elevation, I can not see why they would refuse you insurance.
You should also check the Statutes or with whichever State agency is in charge of regulating insurance companies and find out what remedies may be available to you.
OK
See my post #173