Just to see what would happen I have tried to drive a tank into the water near a couple of ports and an air base. There seems to be an invisible wall that prevents the tank from driving to far unto the beach. Perhaps there a worry about suicidal tankers or it may be an OSHA requirement but I suspect it's a bug.
Here are the locations:
500536,11,221420,0.3,11.9,-45.0
craterma
FOV = 79.3