It is the weave of the fabric (the size and number of holes) that determines breathability or resistance to air movement. Any woven or knit fabric will breathe - even if the weave is made of rubber strands.
If the yarn on the outside of the garment is thinner than the yarn on the inside of the garment, capillary action will pull water to the outside. The increased surface area (not hollow fibre cores) of the thin yarn gives the water more space to spread out. This type of construction can be used in either Nylon or Polyester fabrics.