Blue70 builds swim-specific wetsuits for triathlon and open water swimming. We don't make freediving wetsuits, and that distinction matters. If you borrow a swim wetsuit for freediving, or buy a freediving suit expecting it to feel like a triathlon suit, you'll fight the equipment from the first dive. A freediving wetsuit is shaped for vertical descents, long breath-holds, and minimal water movement. A swim wetsuit is shaped for horizontal speed, surface breathing, and fast transitions. The distance between those two goals explains nearly every design feature.
Read the Lining First
Swim and triathlon wetsuits usually line the inside of the neoprene with nylon or jersey. That lining helps the suit slide over skin, protects the neoprene from fingernail damage, and makes quick transitions realistic. Blue70 uses Yamamoto neoprene in 38, 39, and 40 cell grades. A higher cell number means more flexibility in the shoulders and arms. Lined neoprene allows a thin layer of water to enter between the suit and your skin. Your body warms that water, and that warmed layer becomes part of your insulation.
A freediving wetsuit often leaves the interior as open-cell neoprene, the raw rubber surface without a fabric lining. When you lubricate it with diluted soap and water, the neoprene seals to your skin and reduces water exchange. That seal keeps the warmed layer close and cuts down on flushing. Less water exchange means more warmth over a long session, but open-cell neoprene demands more care. You can't pull a dry open-cell suit onto dry skin and expect it to slide without lubrication, patience, and smooth handling with your palms instead of your fingertips.
- Lined neoprene: slides over skin, protects the foam, and lets a small water layer warm against your body.
- Open-cell neoprene: seals to skin with soap and water, reduces flushing, and tears more easily.
Open-Cell Neoprene Changes How You Enter the Suit
A swim wetsuit should feel snug on dry land and more comfortable once you are in the water. The lining helps you move inside the suit and adjust the shoulders. An open-cell suit fits closer because the material seals rather than slides. That close fit is part of the performance, but it also means any rushed movement can tear the foam. Fingernails, rings, and sharp pulls cause most of the damage at the start of a session.
Freedivers learn to roll the suit up the legs and torso instead of yanking it into place. Swimmers can use the same habit on lined suits. Blue70's care guidance calls fingernail punctures and heel tears the two most common ways swimmers damage a new wetsuit. Open-cell freediving suits raise that risk because there is no fabric layer protecting the neoprene.
Buoyancy at the Surface Becomes a Problem at Depth
Swim wetsuits are built to lift your hips and legs toward the surface. Buoyancy equals speed. In triathlon and open water swimming, good body position reduces drag and helps you move horizontally with less effort. Freediving turns that principle sideways. A freediver starts at the surface in a vertical position and wants to descend without burning energy fighting the suit's lift. The buoyancy that helps a triathlete swim flat makes a freediver carry extra weight on the belt to get below the surface.
Pressure changes the picture. At ten meters of seawater, pressure is about twice the surface pressure. Boyle's law describes the relationship: for a fixed amount of gas at constant temperature, pressure times volume stays constant. Neoprene is not an ideal gas, but the foam compresses as depth increases. The suit loses volume, and its buoyancy drops. A freediver who is neutral at ten meters will float at the surface and sink below that depth. Thickness and placement set the starting buoyancy. Thick chest and torso panels keep the diver warm but add more lift near the surface.
Hoods and High Waists Exist for a Reason
Freediving suits commonly use two pieces: a high-waisted pant and a hooded top or full jacket. The high waist adds a double layer of neoprene over the core and stops the top from riding up during a duck dive. The attached hood matters because the head and neck lose heat quickly in water, and because a hood prevents cold water from flushing down the back as you swim toward depth. A hood also changes equalization and hearing. That part belongs to freediving instruction, not wetsuit fitting.
A triathlon wetsuit has a low, unhooded neck. That shape exists for a reason. Surface breathing, fast rotation, and quick transitions demand a neck that doesn't restrict movement or trap water. For a vertical dive, that same neck is the wrong shape. Understanding that tradeoff helps swimmers see why a purpose-built cold water swim suit fits differently from a suit borrowed from another sport.
The Skin Seal Lesson for Cold Water Swimmers
You don't need to freedive to use one insight from freediving wetsuits. The skin seal matters. In cold water swimming, the difference between a comfortable hour and shivering at the exit often comes down to how much water flushes through the neck, wrist, and ankle openings. A freediving suit reduces flow by sealing open-cell neoprene to the skin. A swim-specific cold water suit reduces flow through a better pattern, a lower neckline, and a thermal lining. The warmed layer stays close to your body instead of flushing out through the openings.
Blue70's Thermal Reaction is built for cold water swimming. It uses a Zirconium jersey lining, a synthetic wool surface designed for added warmth. The physics is similar to the freediving approach: keep the warmed layer close, reduce flushing, and protect the core. The execution differs because the athlete is horizontal, breathing at the surface, and swimming for distance.
- Below roughly 56 to 58 degrees Fahrenheit, a purpose-built thermal suit starts to add meaningful warmth.
- Above roughly 70 to 72 degrees Fahrenheit, a full suit can feel too warm over longer swims, and a sleeveless suit or swimskin becomes more practical.
Where Blue70 Fits
Blue70 doesn't make freediving wetsuits, and we won't pretend a triathlon suit is a substitute. If you are an open water swimmer or triathlete looking for cold water protection, the Thermal Reaction is the model in our line built for that job. If you plan to freedive, invest in proper instruction and a suit built for apnea. The wetsuit is one part of a larger system. Your buddy, your weighting, your equalization, and your surface protocol matter more than the neoprene.
No wetsuit is a personal flotation device. Freediving carries real risks, including shallow-water blackout and barotrauma. No wetsuit changes those risks. Take a certified freediving course, train with a buddy, and stay within your limits. If cold water swimming is your next step, the Thermal Reaction collection is the place to start. Happy swimming.
