Suit Diving - The Promise of Staying Warm
The first thing I learned about diving dry was that a dry suit does not
always keep you warmer in the water than a wetsuit. Most of the dives my
beginning students do are in the 30 to 40 foot (10 to 12 meter) depth range. At
these shallow depths, I did not notice that I was staying any warmer in the
water when I was in my dry suit.
Here is why. Depending on the dry suit you select, the suit itself does not
keep you warm. Trilaminate, vulcanized rubber, coated fabric, and even crushed
neoprene suits have little insulating properties. Dry suits made of these
materials require the diver to use an undergarment and add air or argon to the
suit to stay warm. Undergarments come in various thicknesses like wetsuits, and
the diver selects an undergarment for staying warm in a similar way to selecting
a wetsuit. The warmer the undergarment, the more protection the diver has from
Staying warm below
The problem with neoprene, of course, is that it is highly compressible.
Therefore, the deeper a diver goes, the more the suit compresses and the colder
the diver gets. To avoid hypothermia, the diver needs a thicker wetsuit for
deeper dives. On the other hand, this is the advantage of the dry suit. Most
dry suit material is non-compressible at depths a diver is likely to go to.
After selecting the appropriate undergarment, all the dry suit diver needs to do
is add air to the suit during descent to stay warm. More air will need to be
added to the suit the deeper the diver goes, but assuming the diver adds air the
insulating properties of the suit and undergarment will stay the same regardless
of whether the diver is at 30 feet (10 meters) or 130 feet (40 meters).
The point is, do not expect to be warmer diving in a dry suit if your dives
are at 30 feet (10 meters) or above. A dry suit has the advantage over a wetsuit
on deeper divers, so divers routinely making deeper dives will certainly stay
warmer in a dry suit.
Staying warm up top
Getting out of the water is where dry suits also hold a significant
advantage. In areas where air temperatures are cool or wind speeds are high,
being wet when you get out of the water can be very unpleasant. I was on a
recent trip to the Bahamas where wind speeds hit 40 knots and air temperatures
never climbed past 70°F (20°C). Even though the water was warm, getting out of
the water was very unpleasant. Between dives, everyone was cold and miserable.
This meant that most divers chilled in the water far sooner on their dives as
they had lost a great deal of body heat before starting their dives.
Imagine what happens when you get out of the water and you are dry, however!
Or when you always get into a suit that is dry! Surface intervals become far
more comfortable. You can make more dives in a day because you are not losing
heat between dives. And packing up at the end of the day is no problem. Even
when air temperatures dip below freezing, diving becomes doable when a diver is
dry before and after the dive. This is a huge advantage that a dry suit has over