Finisterre’s Nieuwland 5mm Hooded Wetsuit is a winter ... warm in the bitterest British weather. I found the Nieuwland kept me snug for hours in 9°C Cornish water, with noticeably reduced ...
It’s a pretty exhaustive tome, but the highlights include: Maximum permitted thickness of neoprene is 5mm. Minimum water temperature at which wetsuits are optional is 14°C.