[Twan]

If you want to try a water nation like the ones you like, Atlantis is a good choice in all ages too (in Early of course, it's one of the best thug nation, with lot of high hp/good prot leaders, but in MA or even in LA the big mages/good hp leaders can become above average thugs, and in all eras summoned Sea Kings are also a good base).

ps : but note that sea nations aren't at all a challenge against most AIs, land computer nations are very unefficient at invading seas, you'll just have to worry about other sea powers