From the Avalanche Press website:
Great War at Sea
The First World War took place on all of the world's oceans, from the huge battles in the North Sea between fleets of battleships to commerce raiding in the Indian Ocean. We cover all of these — plus some conflicts that never actually happened beyond the plans of naval staffs — in our Great War at Sea series. Each boxed game covers a campaign or theater of war, with multiple scenarios, or separate game situations, based on the missions undertaken there.
Each scenario lists the ships available, the goals each player needs to achieve in order to win, and the amount of time available. Battle scenarios cover clashes between surface ships and can be resolved in an hour or two; operational scenarios are based on historical missions and can take much longer. Missions include amphibious invasions, convoy escort, commerce raiding, shore bombardment and more. Players find enemy fleets and stop them from accomplishing their missions, while achieving their own ends.
The operational map covers the theater of operations and is divided into square zones, offset in a “brick” pattern. Each zone represents an area approximately 32 nautical miles across. Players form their ships into fleets and move them on this map. Their moves are pre-plotted on log sheets, so that a player does not know what the enemy has done. Even though the player can see the enemy fleet marker on the map, he or she still must determine whether its ships are spotted by friendly ships. If this occurs, play moves to the tactical map, where battle takes place.
Ships are rated for primary, secondary and tertiary gunnery (big, medium and small) and torpedoes. They maneuver on the tactical map and fire on each other with these weapons. Ships are also rated for size and armor. Heavy armor can only be penetrated by torpedoes and primary guns, light armor by those plus secondary guns, and areas with no armor can be damaged by all weapons. When a ship loses all of its hull boxes, it sinks.
Other aspects of the game include submarines, aircraft minefields, motor torpedo boats and still more. It’s not a complicated game (most game functions involve rolling a 6) but it does simulate a rich tapestry of naval history.