Kohlar the Unkilled
Time for some ale
Let us not confuse physical strength with athleticism. While it's true that swimming builds strength, one would never expect an Olympic swimmer to match the strength feats of a Norwegian or Icelandic strongman. Just as one would expect that same strongman to drown (or get stuck) in Black Marsh by not being adapted to that environment. I'd give Argonians the edge in athleticism, with Nords being the stronger of the two physically. 
