Quatney,
I find that with my style of playing CivII, a navy is absolutely essential. I really enjoy doing D-Day type invasions in the game and landing troops and doing shore bombardments, and later in the game conducting large scale bombing raids from offshore carriers.
In a game I played a couple months ago, I was fortunate enough to get extremely powerful and developed a huge navy. I had several small continents in the southern hemisphere and I surrounded them (not each individual island, but the whole group) with a chain of ironclads that were each 3-4 squares from eachother; the idea being that nothing could get through without me seeing it. As I took over more small continents and islands, I just moved my chain to encircle it, and built more ships if necessary. Since I had Leo's workshop, it was nice when they all became destroyers.
I then saw a large continent in the southern hemisphere that I wanted to take over. It had about 10 French and Roman cities on it that I wanted. I built two large invastion fleets to strike the island; one fleet striking the south, and the other fleet striking the east (the western part of the land was uninhabited). This was a very fun thing to do, for I did not strike until I knew my fleet was almost unopposable. By the time the fleets were ready, each of the two fleets had about 8-10 transports full of tanks and marines, escorted by 5-6 destroyers, 6-8 aircraft carriers full of mainly bombers and missiles, 4-5 battleships for each fleet, and 3-4 subs moving farther ahead to sink any opposition, which was minimal. When these fleets bombarded the coastal units and cities until there was nothing left, the marines and tanks swept across the continent toward the north. It was rather easy because each city I took over could then produce more tanks. The 3 cities in the north hung on longer than expected, but I sent over a couple more carriers from my homeland which took care of them. When the continent became mine, I owned the whole southern hemisphere, so I had to move my destroyers to include it. This caused me to basically have an unbroken line of destroyers along the whole equator. When you think of what it would take to do that on planet earth, this is rather impressive. I went on to win this game, although the war turned nuclear. As nuclear attacks got closer to my homeland, I was able to build the spaceship and land on Alpha Centauri in the year 2016.
As you can see, I use my navy heavily, and I like to have a strong one.
The Edge