Original illustration of the Navy Mark V Diving Helmet, in continuous service from 1916 to the mid-1980s — nearly 70 years. A fully rigged Mark V weighs about 55 pounds; rare "gas hat" versions were later adapted to mix helium and oxygen, letting divers go far deeper than a standard air hat allowed.

50% pre-shrunk cotton, 50% polyester. Fabric weight: 8.0 oz/yd² (271.25 g/m²). Air-jet spun yarn with a soft feel and reduced pilling. Double-lined hood with matching drawcord. Quarter-turned body to avoid crease down the middle. 1×1 athletic rib-knit cuffs and waistband with spandex. Front pouch pocket. Double-needle stitched collar, shoulders, armholes, cuffs, and hem.