Yes, it comes down to man vs. shark so that the drag factor is more important than fabric weight in creating faster movement through water.
The human body is covered with uneven skin which has pores to give it ventilation (and hairs which swimmers may wish to shave off to produce better competition times).
Sharks' bodies on the other hand are entirely covered by placoid scales which create tiny vortices to reduce drag in water and so make their swimming more efficient (and quieter - important in seeking prey as sound carries so well underwater).
This article was written a few years ago when Speedo were trying to go even further with an improved LZR Pulse fabric:
http://memagazine.asme.org/articles/...kskin_Suit.cfm