The most obvious way to reduce drag in the water is put bubbles between you and the liquid. That is what penguins do and that is why they can swim so fast.
From National Geographic:
The key to this talent is in the penguin’s feathers. Like other birds, emperors have the capacity to fluff their feathers and insulate their bodies with a layer of air. But whereas most birds have rows of feathers with bare skin between them, emperor penguins have a dense, uniform coat of feathers. And because the bases of their feathers include tiny filaments—just 20 microns in diameter, less than half the width of a thin human hair—air is trapped in a fine, downy mesh and released as microbubbles so tiny that they form a lubricating coat on the feather surface.
I am confident that filaments such as these could be easily be recreated for swimsuits of today but will Craig Lord allow his "b****", also known as FINA, to approve it? - I think not.