Notes about things regarding scuba diving that I have come to know.

Diving Wet When It Is Cold

For diving to be enjoyable and safe you need to stay warm. Being cold promotes stress, lowers performance and leaves you susceptible to DCS. Everyone's tolerance to cold is unique. For some bizarre reason I tend to find the second dive more comfortable. It's easy to say that diving dry is the way to go when it is cold but logistics, finance, training and a number of other factors sometime dictate diving in a wetsuit.

Anyone can manage a wetsuit dive when air and water temperatures are over 65 degrees Fahrenheit. As the mercury drops things get to be a little more challenging. Many divers cite 50 degrees F as the low end of wetsuit diving. Most can go a little cooler but prefer not to and will pass on diving or dive dry when it gets to be that cold. These colder temperatures may also leave you fatigued and willing to sit out a second dive of the day.

This feature will describe some techniques that can help you get the most out of diving in a wetsuit when the temperatures are becoming a challenge. The gamut of temperatures varies a lot with the water sometimes being nicer than the air or the water may be frigid while it is toasty topside. Adapt these tips as you find appropriate.


  • Staying warm requires that your body have fuel to burn. Don't go nuts eating but this is not the time to starve yourself.
  • Consider setting your rig up at home. This can be more fun than at a cold windy dive site. Sort the gear you will use from all that other contingency stuff.
  • Arrive at the dive site warm and comfortable. If it means wearing a sweater or driving with the car heater on then do it. Don't arrive with a thermal deficit.
  • It's never too early to be drinking hot fluids. Avoid excessive Caffeine.
  • Once you are at the dive site say warm with adequate clothing and a hat and gloves if needed

Gearing up to Dive

  • Your wetsuit needs to fit well. A 7mm suit with 2X on the core (thighs, groin and torso) is considered standard. More on that here.
  • Your booties should be 6-7mm neoprene. Seriously consider adding 1-2 mm neoprene sock inside.
  • Gloves want to be of a gauntlet style that will extend well past your wrists. This style reduces water exchange and places lots of insulation on your wrists where blood runs close to the surface. Cold hands are hazardous and are the cause of many cold water dives ending sooner than desired. There are 3 finger "lobster claw" gloves that some like. I have done well with 5mm 5 finger gauntlet gloves.
  • Bring some warm water. This water wants to be good and warm but not hot. If it's too hot it will trick your body into cooling itself when you don't want that happening. I like to use refilled liter drinking water bottles in a cooler. If I'm heading straight for the dive site I will just roll 6 bottles tightly in a towel and pack them in the car. For a longer day I heat the cooler shell by filling it with hot water then after adding the filled bottles fill it way with hot water to increase the thermal mass. Others use a collection of picnic jugs, it's all good. More on using the water is coming up.
  • So you are now in your wetsuit and you have pulled your socks and booties on. Pour some of that hot water into the socks and booties before zipping up. The concept is that water will enter your suit. You can let Mother Nature fill the gaps with frigid water or you can beat her to the punch with something delightful. Fill the socks and booties way and they will probably overflow as you zip them and your suit legs.
  • Before or after donning your rig prime your suit. Pour 2 bottles down the neck. Be sure to sway side to side so you feel it go down your arms to the wrists. Again you are getting warm water in there before the cold stuff can enter. By priming the suit you can make entering frigid water hardly noticeable.
  • As much as possible keep your hands and the outside of your suit dry to limit evaporative cooling. Keep a towel handy.

Sodium Acetate Heat Packs

In addition to priming your suit diving with a sodium acetate heat pack can do wonders for your diving comfort. Generally they are worn in a cummerbund under your wetsuit and wrap around your back and kidneys where they help to warm you and your circulating blood. The sensation is not unlike diving in a hot water bottle. Sodium acetate is a non toxic liquid that is stable at room temperature even though it wants to freeze at temperatures below 130F. The liquid is contained in a pouch that also contains a concave metal disc. When the disc is pressed it snaps and the resulting motion causes a few molecules to freeze and soon the whole pouch is doing the same thing. Since it freezes at 130F that is the temperature at which it releases heat energy as it changes state. At the end of the dive they can be boiled in a pot of water for about 10 minutes and this will thaw the material for re-use. Here is a more thorough explanation of the process

Generally they remain hot for a little over an hour. This is enough time to gear up and enjoy the benefit for a nice hour long dive. If your dive runs even longer you will not be as thermally depleted at that time you will have the stamina to enjoy the end of the dive. Since it is a fluid filled pouch depth has no effect. If one were to rupture it is a harmless non toxic material.

There are also some smaller versions that are helpful to warm hands between dives. Remember that these will reach 130F and that can be very uncomfortable on the skin. Cummerbunds will have a thin neoprene layer that insulates your tender abdominal skin from direct contact.

During the Dive

    Stay synchronized. You don't want to be in the water while your buddy is still getting his or her act together up in the parking lot.
  • Diving with grace in an effortless fashion is a beautiful thing. Unfortunately that sort of effortless diving does not do much to keep you warm. Don't be afraid to pick the pace up a little.
  • You will notice certain motions tend to introduce cold water into your suit. They will vary with suit, body and fit but you will soon find out what they are for you. Avoid those motions.
  • As much as we said to pick up the pace avoid thrashing and flailing with your arms. That motion tends to pump water through your suit costing you thermal energy.
  • Flex your fingers. Often your fingers have nothing to do and are inactive. Flex your hands periodically. Generally your palms will warm the water in the palm of the glove. Flexing will distribute that heat to your fingertips. For this reason cold water gloves do not want to be terribly tight and a little extra volume in the palms in a good thing.
  • Pay attention to your body and recognize that getting out of the water will take time. Don't push yourself and keep an eye on your buddy. Cold water dives will not be your personal best for runtime and that is fine.

Surface Interval

  • Evaporative cooling is the enemy. Get out of the wind and at a minimum get out of your wetsuit from the waist up. In severe conditions prepare to completely get into dry clothes. Standing around in the breeze while wearing wet neoprene will rob your body of much energy.
  • While still in your wetsuit you can pour more of that hot primer water into the suit to displace any cool water.
  • Once out of the neoprene get into a warm shirt and / or sweater and get away from the wind if you can.
  • A dive parka can be worn. This is an oversized trench coat type of garment made of water tolerant materials. It can be worn over a wet or drysuit to provide shelter from the wind.
  • Eat a good high energy snack and down some hot liquid beverage
  • Soaking gear, especially hoods and gloves in a cooler of hot water can make getting back into them much more comforting.

After Diving

  • You may choose to get out of your suit and dressed before breaking your gear down for the day. An old raincoat will help you stay dry while tending gear.
  • Enjoy more hot beverage and keep a drying towel handy.
  • Getting out of your wetsuit and changing can be the most difficult part of the whole outing. Do this before you take a beating from evaporative cooling. Prime your suit just before peeling it off. Have your towel and clothes ready and just do it. Once you towel away most of the moisture it gets surprisingly easy.
  • Go get a nice meal and feel good about getting out to challenge the environment. It sure beats watching TV.

I hope you found a few ideas that will make your cold water diving more enjoyable. While written to help divers extend their wetsuit diving season many of these tips are applicable to drysuit divers as well.

This page created 9/25/2008