Maximizing thermal protection whilst minimizing buoyancy, the Halo 3D has body-mapped insulation, strategically placed to enhance protection when in horizontal trim. Designed for use underneath membrane and trilaminate drysuits. Convenient zipped sleeve pocket, full-length double-headed zip with an internal and external zip cover, thumb loops to aid donning, secure foot stirrups to prevent legs riding up, simple one-piece design, machine washable and quick-drying. The one-piece design is simple and functional; lower profile around the hips and midriff, allowing high maneuverability with panels of additional thermal protection layers located where they are needed most, enhancing the thermal protection in critical zones without excessive bulk. It can be worn as part of a layering system with Xerotherm and in extreme cases, even Arctic.