The Seal Lion PLUS underwear is definitely the warmest underwear from the series. It was created for very long dives in extremely cold waters. The underwear consists of three layers. The top layer is made of Polartec® Wind Pro®, the middle layer is made of Polartec® Thermal Pro® material. The fabrics used are breathable and have very good thermal properties. The cut and the used stretchy materials prevent any restriction of movement.