World War One was a war in which Entente navies played their part in the defeat of the German Empire. The largest navies on both sides were Britain's Royal Navy, and the Imperial German Navy. As such, the naval war was largely between these two navies.
As the war began in 1914 the first naval encounters were not long in coming. In 1914, the Royal Navy and Imperial German Navy first met at the Battle of Heligoland Bight. The Battle of Heligoland Bight was a clear victory for Britain's navy as they wiped out much of the German fleet.
Germany's defeat in this battle convinced the German High Command that the Imperial German Navy was unlikely to win further surface fleet battles with Britain's navy. As such, the fleet returned to port and remained there until 1916. For Germany, the war at sea was not considered essential to victory.
However, the Royal Navy played a more important part in Britain's wartime strategy. With Germany's navy remaining in port, the Royal Navy stepped up its German economic embargo. This economic embargo had an impact on German food imports and munitions as supply shortages increased. In addition to this, Britain's navy also played its part in transporting troops to allied France and in supplying Russia. In fact, the Entente planned the Gallipoli Campaign to establish a better supply route to Russia; but Britain and France wrongly calculated that their own navies would be enough to secure the Dardanelles Straight.
In 1916, Germany reconsidered their naval strategy. Scheer suggested that the navy could be used to gradually break Britain's economic blockade, so the German navy planned the Battle of Jutland. This battle was the largest naval battle of the war, and one that neither side could claim a genuine victory. However, Britain's blockade continued after the battle; so in that respect it was more of a victory for the Royal Navy.
The Germans turned to U-boats as an alternative to surface fleet battles. With the U-boat the Germans aimed to begin their own blockade of Britain, targeting British merchant shipping with unrestricted submarine warfare. If the Germans could sink enough merchant ships, this could defeat Britain in a matter of months.
Consequently, Germany began their U-boat campaign in 1917. At first, Britain's merchant shipping losses increased markedly. However, as Britain began to better organize the defense of the merchant ships with convoys these losses began to decrease to more acceptable levels. The U-boat campaign failed to defeat Britain, which would have implications for the outcome of the war.
Not only did Britain's blockade continue unabated, the USA had joined the side of the Entente during the U-boat campaign. The war at sea was now largely lost, and the war at land would likely be lost too if Germany could not break the Entente lines in the West soon. With U.S. reinforcements increasing in number, both sides made their final advances in 1918. Germany's final advance was gradually halted, and then pushed back by the Entente armies. Then the war was lost for Germany.
Navies had played an important part in World War One. Britain's economic blockade limited German supplies, and Germany's losses at the Battle of Jutland and Helgoland Bight further Highlighted Entente naval superiority. The U-boat campaign was also one of the war's turning points, as Britain remained undefeated and it also ended U.S. neutrality in the conflict. The Entente, therefore, had the advantage in the war at sea; and this advantage was one factor in their eventual victory.