User blog comment:DevilWarrior112/Altair vs Ezio/@comment-1411936-20100128122745

Most people take into account gameplay mechanics, save for weapons as weapons are cool. It is stated in the extended manual of Assassin's Creed II that Altair can't swim because of a bug in the Animus 1.0. Altair was smarter, but despite his skill, cannot swim because of aforementioned bug.