Gunwhale

Naval The name (pronounced GUN'L) given to the uppermost line of planking of a boat's sides. In the old ships the upper tier of guns used to fire over the top planking which was therefore specially strengthened by 'whales'.
Found on http://www.britishempire.co.uk/glossary/g.htm

Gunwhale

Top side of a boat.
Found on http://www.encyclo.co.uk/local/20645
No exact match found