Building and structure setbacks.
A. 
All buildings and structures shall be set back at least 50 feet from the ordinary high-water mark.
B. 
Reduced principal building setback. A setback less than the fifty-foot setback required from the ordinary high-water mark shall be permitted for a proposed principal structure and shall be determined as follows:
(1) 
Where there are existing principal buildings on each adjacent lot, the setback shall equal the average of the distances the two existing principal buildings are set back from the ordinary high-water mark or 35 feet from the ordinary high-water mark, whichever distance is greater.