Nathan Drake's brother Sam had to do something to keep him busy during all those years of not being dead (and never being mentioned in any of the other games). Evidently he chose to study the art of levitation, as captured in Uncharted 4 by Reddit user IzeBerg.
Look at poor Nate doing the old shimmy-and-climb routine while Sam ascends with little more than a "Sim Sala Bim!" Becoming a master of the art of illusion could also explain why no guards ever seem to notice him.
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