Seems that you are biased a little bit now Aezeal
Been aquatic is an advantage but has a price. Armour of aquatic units is usually quite bad, UW recruitable mages are scarce and magic diversity is hard to achieve. Land nations say things like "You are aquatic, going out of land is declaring war" and such.
So 1/5th should be more or less the right number fro 5 players.