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How thick of a wetsuit do I need?

How thick a wetsuit do I need?

This is a great question with no easy answers! There are many variables, beyond being a unique individual, that impact the answer. Factors include individual tolerance, water temperature, heat loss areas vs. suit thickness and fit, the length, depth and number of dives, surface conditions and the type and style of suit. Let's look at these factors in more detail. While we focus on wetsuits here, don't forget that dry suits have a place in recreational diving too. A dry suit excludes all water and insulates with air. The suit is more bulky but allows you to interchange various types of undergarments.

Individual tolerance

The fact is that Mother Nature made us all different. Women will chill faster than men no matter what rumors you've heard. Women do have that extra subcutaneous fat to protect embryos but that doesn't mean it provides extra warmth. Women also have a higher surface area to mass ratio which basically means they have a better cooling system than men. Have you ever worked in an office building where the women are cold at temperatures men find barely comfortable?

Water temperature

To state the obvious, you will lose heat faster as the water gets colder. Remember how your wet suit works. There are bubbles in the neoprene which help insulate you against the cold water outside the suit by trapping a thin layer of water around your body. The water does flow, but slowly, so your body heats it but that it also dissipates your body's heat into the water. You can't heat surrounding water so you will chill eventually. The colder the water, the faster you will chill. There are waters such as the North Atlantic or Lake Superior where an unprotected person in the water will die in a matter of a few minutes from extreme hypothermia.

We don't think much about hypothermia in the tropics but you have to understand that hypothermia can still be a factor even in the warm and sunny tropics. Some areas of the Pacific are affected by currents that bring cold water down even the days are warm and sunny.

Heat loss areas

The three major heat loss areas are:

1. Inner thighs (near the femoral artery)
2. Under the arms (near brachial artery)
3. The head and neck (60% of heat loss is here!)

If you have lived or grown up in colder areas you should know all about hats and heat loss. Diving in cold water without a hood is sort of like having the heat on in the dead of winter and leaving the front door and windows wide open. The fit of the suit is also important, especially under the arms and around the thighs. You don't want areas for water to collect.

Thickness and fit of suit

A very simple rule is that the colder the water the thicker the suits needs to be. Increasing the thickness of the suit, or adding layers of neoprene, helps reduce your rate of heat loss. If you chill faster than others wearing similar suits you may need a thicker suit.

The better your suit fits the less water flow it will allow and the warmer it will keep you. Remember that the water around you is always lower than your body temperature so you will chill eventually. If the suit doesn't fit, there's no value in wearing it.

When we talk about thickness of the suit remember the neoprene sheets are measured in fractions of an inch. Suits today are mostly measured in millimeters so there is an approximation or even "rounding" which may cause a suit ¼" thick to be listed as a 6.5 or 7mm suit. Here is an approximate chart for comparison:

Length and number of dives

Heat loss is cumulative. The longer you stay in the water and the more dives you make the more heat loss you will have. If you will make mostly shallow dives with a lot of bottom time, your heat loss will be greater than that of a deeper dive for a short period. If you make two or more dives in a day, the heat loss problem grows.

Depth of dives

Since wetsuits are made of neoprene with millions of tiny bubbles, those tiny bubbles compress as you go deeper. In other words, the deeper you go the more the wet suit compresses and the less it will insulate. If you routinely dive deep you may want a thicker suit than if you dive shallow.

Surface conditions

While not compressing your wetsuit the weather on the surface plays a big role in how warm you stay. If it is cool, overcast and windy you will be colder and will need more surface interval time between dives to regain that lost heat. You will always begin to warm on the surface but you may not recover enough heat to make your next dive comfortable.

Type and Style of suit

There are several basic types of suits to consider:

1. Short sleeve shorty
2. Long sleeve shorty
3. Jumpsuit
4. Wear a jumpsuit with a shorty over it
5. Two-piece Farmer John or Famer Jane for women
6. Drysuit
7. Consider integrated hoods as the suit gets thicker

The style you buy has a big impact on how warm you will be. Each type has advantages and disadvantages depending on the type of diving you are doing and the water temperature. Divers will sometimes wear a 3mm short sleeve shorty over a 2 or 3mm one piece jumpsuit. This provides greater protection over the torso area and also still provides a lot of freedom for the legs and arms. A Farmer John type suit doubles up the thickness on the torso by the suit design (long sleeve jacket, bibbed overall type pants). Consider a hood as they too come in various thicknesses and designs from a simple, thin swim cap type hood to a thicker hood integrated with a bib or even a vest with a hood. Remember that 60 percent of your heat loss in water is from your head and neck.

Tips

• Wet wetsuit to put on? Put a PVC bag on your leg or arm and you can push your limb through quickly and easily.
• Wet wetsuit to put on? Have a dry rash guard in store? Put it on before you get into a wet wetsuit and you won't feel the cold neoprene on your body.
• Wearing your booties tucked inside your pant leg will help keep you warm.
• You can "prime" a wetsuit with warm to hot water before entering really cold water.
• Bring along something warm to drink after cold water dives or on cold days. Try hot jello!
• If you are diving in cold water make sure you are rested, allow time to rest and re-warm before you dive again.
• If you ever get to the point where you are shivering that is your body attempting to re-warm itself. It's time to get out of the water and allow ample time to warm up.
• Give your body fuel to work with. Eat a good meal!