5mm vs 7mm Wetsuit: Which Thickness Is Right for You?
Choosing between a 5mm and 7mm wetsuit trips up more divers than almost any other gear decision. In this episode, Ray Hollister draws on 8,000 dives across four decades to break down exactly when each thickness makes sense—and why the cozy feeling in the dive shop often leads to the wrong purchase. Whether you're planning tropical reef dives or exploring cold water wrecks, this guide helps you match your suit to the actual conditions you'll face so you stay comfortable without wasting money.
Key Takeaways
- Water temperature determines your starting point. A 5mm suit works best in 70 to 80 degree water, while a 7mm is built for 50 to 70 degrees. Think of it like choosing between a light jacket and a heavy coat based on the weather forecast.
- Thickness is only half the story. A cheap 7mm suit with poorly sealed seams can leave you colder than a quality 5mm with good construction. The stitching matters almost as much as the neoprene itself because bad seams let cold water pump through like tiny leaks in a window.
- Wetsuits lose insulation as you go deeper. At 100 feet, your suit compresses and loses about 60 percent of its warmth. That thick 7mm effectively becomes a thin 3.5mm suit, which is why serious cold water divers often switch to drysuits.
- Thicker neoprene costs you movement. Every extra millimeter makes it harder to reach behind you, kick efficiently, or adjust your gear. A 7mm suit can turn simple underwater tasks into a workout, especially for newer divers still learning good technique.
- Your body type affects warmth more than specs suggest. Lean divers often get cold faster and may need thicker suits even in warm water, while larger divers with more natural insulation sometimes stay comfortable in thinner neoprene at surprisingly low temperatures.
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Henderson Hyperstretch Wetsuit
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