I thought I'd try the Very Hard setting, having beaten every difficulty level before it easily enough. The only one left after says Impossible Hard, so I assumed maybe it was impossible. Anyway, the AI doesn't expand too quickly. Maybe the negative health thing bothers them, so the AI avoids doing that. Even if your health is in the red, you are still better off by having more bases everywhere.

I learned that using covert operators to Recruit Defectors, gives you not just one new unit, but several at once. So good way to build up your army.

I was once again able to get spy headquarters far sooner than any AI. I'm surprised that even when I had agents in headquarters to increase the chances of success, and with no one having any counter agents, I still had such a high rate of failure when it came to stealing technology. Wish I knew the exact stats of how much everything affects everything else.

Once I remembered there was a virtue that gave you science for killing aliens, and worked my way to it, I went around with my boats killing things from the shore, there plenty of alien nests about. I started with the bonus to see where the alien nests were at. By having a group of ships near each other, should any sea dragons appear, they can be easily eliminated.

After getting what I needed, I focused on technologies that gave me Supremacy bonuses. Leveling up in Supremacy gives free roads, and keeps giving you far superior military units.

A melee unit that is embarked(in the water) can attack a base, and fight from the water to capture it effectively. I had my ships knock its hit points down to 1 first of course.

By choosing the Advance Settings option to not just have to capture the enemy capital, that just too easy to take on one city, I had to take on all of their cities. After that was done, it still didn't end though. I had to destroy all of their units. The only unit left was a Worker, so I had two ships open up on it, and destroy it, then game won.

I guess I'll try the Impossibly Hard setting next, just to see.