The SinNature must be destroyed and replaced with a NewSpirit which exists in the KingdomOfHeaven.<p>The KingdomOfHeaven is the SpiritRealm, which is a dimension of existence higher than that of the space-time continuum in which all physical life exists.<p>It is not possible for the purely physical to exist in the SpiritRealm. This is why we must be born of the Spirit.<p>Being BornOfWater means being born into humanity. Angels cannot experience the KingdomOfHeaven in themselves as BornAgain humans may Luk 17:21.<p>If there is any confusion about the birth by water being WaterBaptism the next verse clears it up.  He connects the water with the flesh.