There should be more Naval Units and they should act more like the Combat system of the land units, The Rock/Paper/Scissors style Eg - Spearmen beats Chariot, Chariot Beats Axemen, Axemen Beats Spearmen. It should be more like this in the Navy especially in the early Ancient Ages where there's only 2 Ships, Gallies and Trireme. Basically If you want to rule the Seas in the Ancient Age on an Archipellago map all you have to do is get circum-navigation and mass produce triremes, they have no counters. I believe all navy Units in their Age should have counters. Currently in the Civ4 Game there are no counters from One Navy Unit to another except for Strenght and for a Trireme having 50% over Gallies. Sea Warfare should be similar to land warfare on Civ4 This is just an Example but it should be something like Battleship has an advantage over Destroyers, Destroyers have an Advantage over Submarine, Submarine has an advantage over Battleships. It would make Civ4 Sea warfare much more interesting and flexible. More Ships should be added in the Ancient, middle and Industrial age to peoperly use and balance out this Combat System for the navy. Maybe also add a Navy Unit capable of collateral damage to prevent Navy SODs, I know Battleships can do collateral damage but it should be avaliable in an early age.