Reportedly weighing in at up to 105 grams, the cased-in-carbon Luminox Carbon SEAL 3800 Series is a diver’s watch, water resistant to 300 meters. Yes, it is under 100 grams in some versions, which is remarkable for what is a 46mm tough ticker. We have not done any comparative tests but this might well be the world’s lightest diver’s watch (quartz category). Ok there is no such award or category but if there were, Luminox would have a winner on its hands. Ok, so it is not completely cased in carbon. It has a steel caseback protecting its reliable quartz Ronda 715 HH6 heart but the carbon compound process used to create the (rest of the) case looks impressive. Steel is also used for the crown.