But if you want to become a cold water swimmer, you need to be prepared for the temperatures and aware of the risks. Leading neuroscientist Dr Rachel Taylor, who has teamed up with outdoor equipment brand Red, has shared her 'golden rules' for cold water swimming. Optimum time: Dr Rachel advises those starting out to spend between 20 - 90 seconds in cold / ice water, followed by wrapping up afterwards with a warm drink. Don't shower instantly, as this can send your body into shock.