Board Thread:Warhammer 40k General Discussion/@comment-7499389-20130407223055/@comment-66.120.29.153-20130410210045

Can a space marine swim in power armor? can a medieval knight in chain mail?

but out of armor...

Probably not very well. Humans swim well due in part to their buoyancy. A space marine has heavier and thicker bones with a higher mineral content, and a fused rib cage just adding to the bone mass. While they are larger than humans, I'd guess that if we measure by density a space marine is noticably more massive given the volume of their bodies. That being said this is somewhat offset by their increased musculature as well as the multilung acting as an air sac (and also providing more efficient oxygen flow). I'd guess that an olympic swimmer could outpace a space marine, but then again the Emperor designed them for war, not water polo.