Seam construction impacts warmth and comfort. Users in colder areas with water temps below 65 degrees should seriously consider Sealed Seams to keep the warm in and the cold water out. Below is a listing of the 3 types of seams available on wetsuits:
Flatlock Stitching: Recommended for warm water above 62F. You can recognize this seam from the outside. It looks like railroad tracks. The interior and exterior seams look about the same. The interior seam construction is flat and comfortable against the body. Some water may seep in through these seams.
Sealed (Glued and Blindstitched): Recommended for cold water 55F and up. This construction is best for cold water because the seams are glued, then stitched. It looks similar to Flatlock stitching, but is narrower in width. Very little water will seep through these seams.
Sealed & Taped (Glued Blindstitched & 100% Taped): Recommended for very cold water 55F and below. Same construction as above plus interior seam taping. The tape reinforces seams for added durability, and prevents any water from seeping through.
Stitchless Seams - These seams are the ultimate in performance. Stitchless seams eliminate stitching at crucial seam areas to reduce weight, increase stretch, and prevent holes from being pierced in the neoprene. Stitchless seams are also remarkably durable and long lasting.
Wetsuit Wearhouse Video Series: Seam Types Explained