The last picture/pischer card is paying homage to Belgium's resistance to the Germans in 1914. It takes Belgium's unusual victory by inundation to a new psychological level with a little humor.
In October of 1914, the Germans were advancing in superior numbers. The Belgians were on the west side of the Yser River, on higher ground.
From the firstworldwar.com website, "With Belgium resistance weakening and the King, Albert I, fearing a German breakthrough in the direction of Dunkirk and Calais, the Belgians took the drastic step of opening the canal locks at Nieuwpoort on 25 October. The result was the German Fourth Army was obliged to retreat on 29 October transferring its offensive effort to Ypres...Nieuwpoort remained in Belgian hands throughout the war."
So, it was a military and a psychological victory for the Belgians, as they were able to keep approx. 5% of their country out of German hands.