Lycra is 1mm at the most. Lycra suits are not neoprene wetsuits and so they are not designed to add much warmth. Yes a small extra warmth and some wind protection. The main purpose of a lycra suit is to protect from the Sun, stingers, affords some protection from abrasions or cuts when coming in contact the reef or rocks. This OH Blue Camo lycra suit has an additional purpose; it can also be used to wear over your existing wetsuit offering a blue water camo pattern with out having to buy a new blue water suit when making a short BW Hunting trip. note: They add almost zero additional buoyancy Kind regards, Extreme Spearfishing - 02 9907 4911