This type of stitch lasts forever, but is not watertight, and can cause skin irritation or rash because the seam creates a little ridge that can dig into your skin. This is found on the least expensive suits and mainly summer suits. A flat stitch doesn t have a ridge at the seam to push into your skin like the overlock method of joining two pieces of neoprene. It is not as durable as the overlock stitch, but does not cause as many rash problems. But it is also not a watertight stitch.
Water can go through the needle holes.
Blindstitching is flat, no ridge. In the sewing process the needle does not penetrate through the neoprene, so there are no stitch holes for cold water to follow. Double-blindstitched suits have stitching on both sides, neither of which breaks through to give water a path to follow. Naturally, this type of seam is found on only the most expensive wetsuits. Taping reduces flexibility, however.