Fourth Element Xerotherm Undersuit

At a glance

Fourth Element Xerotherm Undersuit is a undersuit from Fourth Element, rated 4.6 out of 5 and placed 6 of 26 in our exposure suits shortlist. Its defining number is weight: Approx. 850g (medium size, one-piece). It scores hardest on bench performance (94/100) and softest on value for money (60/100). The clearest advantage divers report: retains warmth even when saturated with water.

What the undersuit actually gives you

Where it wins and where it costs you

Full review: Fourth Element Xerotherm Undersuit

The Fourth Element Xerotherm undersuit stands as a benchmark in thermal protection for divers who demand serious warmth without unnecessary bulk beneath their drysuits. Constructed from a unique brushed fabric that traps warm air against the skin while wicking moisture away, this undersuit performs exceptionally well even when damp, a critical advantage for divers who encounter minor drysuit leaks or condensation during long or repetitive dives. The fabric's ability to retain insulating properties in wet conditions sets it apart from conventional fleece-based undersuits, which typically lose much of their thermal efficiency once moisture penetrates the material.

Designed with articulated paneling, the Xerotherm undersuit moves naturally with the body, reducing restriction during finning, reaching, and other underwater movements that often feel cumbersome in bulkier thermal layers. The garment features a low-profile construction that fits smoothly under a drysuit without creating excessive bunching, helping maintain buoyancy control and streamlining during descent and ascent. Flatlock stitching throughout minimizes chafing on the skin, while the brushed interior surface offers a soft, comfortable feel during extended wear, whether on a single dive or across multiple dives in a day.

Available in both one-piece and two-piece configurations, the Fourth Element Xerotherm caters to divers with different layering preferences, allowing for customization based on water temperature and personal thermal tolerance. The two-piece design in particular offers flexibility, letting divers mix and match separates for milder conditions or combine them for maximum insulation in colder waters. Reinforced areas at the knees and other high-wear zones extend the undersuit's durability, making it a reliable choice for technical divers, cold-water explorers, and anyone seeking dependable warmth retention as a core piece of their drysuit diving system.