Zip up the O'Neill Psycho-TechWetsuit before hitting the water to ensure you are warm and covered for the duration of the session. The 4/3 thickness lends itself well in cool to cold water and can even fluctuate into warmer temperatures with ease. This versatility is provided by the combination of the Technobutter 3 and Technobutter firewall fabrics that combine to keep water out, move with you, and trap air for impressive warmth.