During the First World War, navies didn't have much of a role as the armies did. The most well known conflicts on the sea were of the British navy against the German U-boat fleet. Another well-known event that happened at sea during the First World War was the sinking of the Briitsh ship Lusitania which led to the Americans joining the war.
Durign the First World War, submarines were first used. They were used to attack the merchant convoys of other countries. During the First World War, the same class type of ships that were used during the Second World War were also used. This includes battleships, destroyers, submarines, cruisers, aircraft carriers, etc. The biggest and most expesnive being the battleships and the aircraft carriers.
During World War 2, the ships were mostly the same as the ones that were used during the First World War but with much more improved with bigger, more powerful guns, faster ships, better submarines and torpedoes, and more. The Pacific Campaign was where most of the naval conflict occured. There were more naval invasions and battles during the Second World War. Also, during the war, the famous Higgins landing craft was first used on the beach landings of Northern France during Operation Overlord. That was one of the most important events during the Second World War because it allowed the Allies to secure their place in France.
Modern ships are equipped with weapons that are superior to any WW2 or WW1 ship. They carry anti-ship missiles instead of large guns. Combined with their more advanced radar, they can fight ships miles away without being seen. Today, the most expensive warships are aircraft carriers. While the battleships were taken out of the navy, aircraft carriers are still used. The country with the most aircraft carriers is the United States with the same amount of carriers in service than the next eight countries combined. Also, the modern landing craft use air cushioning and can land on more coastlines than older landing craft.