For the diver transitioning from other types of diving (such as surfing or SCUBA diving) to Spearfishing, they will typically arrive at a dive store wearing a closed-cell wetsuit, and be under the false impression that this wetsuit will in some way keep them warm while freediving for fish on a single breath of air.
What the two constructions do differently
Closed cell wetsuits and open cell wetsuits are generally made from the same type of wetsuit material. That material is usually some form of nitrogen-blown neoprene of varying densities. The only real difference between closed cell suits and open cell suits is the inner surface of the neoprene. Closed cell wetsuits have an inner surface made of nylon or similar type of material. This allows for easy donning and doffing of the wetsuit, and also helps to prevent wear of the wetsuit. Open cell wetsuits have an inner surface made of raw open cell foam.
Of particular note, the open cells in a good quality open cell wetsuit create suction between the wetsuit and your skin. This creates a very tight fit, often described as being pulled into the wetsuit. This is a major difference between a well fitting open cell wetsuit and a well fitting closed cell wetsuit. Closed cell wetsuits always have a layer of water between your skin and the wetsuit. This layer of water is often in circulation. The open cell wetsuit removes this layer of water and allows the wetsuit to be in direct contact with your skin.
Why the water layer matters more in freediving
Most Scuba Divers are slow moving in the water and therefore do not put as much pressure on their wetsuits as Spearfishers do. A Spearfisher can spend hours in the water doing a variety of activities including, long slow dives to depths of 20m or more, followed by quick sprints to the surface to refuel, and then back to the bottom to repeat the process. Many Spearfishers also spend a lot of time floating on the surface between dives and this can also cause heat loss through the wetsuit.
Warmth, flexibility and flushing compared
| Criterion | Open cell | Closed cell |
| Thermal retention at equal thickness | Noticeably higher, roughly equivalent to 1mm to 2mm of extra lined neoprene | Lower, with continuous water exchange |
| Flexibility and breathing comfort | High, no inner lining restricting stretch | Reduced, lining limits chest expansion |
| Flushing during dive cycles | Minimal once sealed correctly | Ongoing, worsens with poor fit |
| Donning time | Two to four minutes with lubricant | Under a minute, dry |
| Tear resistance of inner surface | Low, fingernails and jewellery cause damage | High |
| Typical service life with regular use | Two to four seasons | Four to six seasons |
Reading the flexibility difference in practice
One of the key considerations for freedivers and spearfishers is the amount of chest expansion that is required while wearing a wetsuit. A closed cell wetsuit, even one that is labelled as 5mm, can restrict the amount of chest expansion that a diver requires. In contrast, a properly sized open cell wetsuit returns a large amount of range of motion, which is why it remains the suit most freedivers and spearfishers end up recommending.
The real costs of open cell
A wetsuit that is to grip for warmth needs to be lubricated. The most common lubricant for wetsuits is diluted hair conditioner. There are, however, specialised products available for wetsuits.
- Mix roughly one part conditioner to ten parts water in a bottle and pour it inside the suit before entry.
- Remove rings and trim fingernails, since the inner surface tears under a point load.
- Turn the suit inside out to dry, and never hang it from the shoulders on a thin hanger.
- Rinse in fresh water without detergent, and repair small tears immediately with neoprene cement before they spread.
Closed cell wetsuits are far easier to wear on land as they are far more resistant to abrasion. This means that they will withstand being dragged over the gunwales, over the rocks and along the boat decks. However, divers who spend most of their time on the vessel or scrambling around on the reef will need to consider this point.
Matching construction to conditions
Water temperature and session length are more important determining factors for preference of open cell or closed cell suits than personal preference.
- Below 18 degrees or sessions over two hours. Open cell, 5mm to 7mm depending on latitude and body composition. The thermal margin is not optional here.
- 18 to 24 degrees, moderate sessions. Open cell in 3mm to 5mm remains the stronger choice, though a well fitted closed cell suit works for shorter dives.
- Above 25 degrees, short shallow work. Either construction performs adequately. Closed cell or a lined-outside open cell hybrid makes sense where boat traffic and abrasion are constant.
- Charter, training or shared equipment use. Closed cell, because rapid donning and shared handling destroy open cell interiors quickly.
The hybrid middle ground
The majority of suits used by serious spearfishers are open cell interior with a smooth outer face (nylon outer face). These suits provide the best of both worlds. The outer face of the suit provides the best possible means of preventing abrasion. In addition, the smooth outer face provides the best possible means of preventing wind chill when on the surface. The inner face of the suit is made of open cell neoprene, the best possible material to keep a diver warm.
Making the decision
In reality, however, the most important consideration when choosing a wetsuit is how it fits. Open cell suits can also flush just as badly as closed cell suits if they are not fitted correctly. So, ideally, divers should be looking for custom-made suits, or even better, off-the-shelf suits that are size-graded. People who are going to be using their suits frequently and going after specific species of fish, as opposed to just taking the occasional dip for relaxation, will get lots of value out of the warmth and flexibility of an open cell suit, provided they are treated with extra care.
