Drysuit (cold-water exposure suit)

A drysuit is a waterproof garment that prevents water from touching your skin. It uses a seal at the neck and wrists to keep you dry.

How it works in practice

The suit creates a dry air pocket around your body. This air acts as your primary insulation while you are underwater. Most divers wear thick thermal undergarments inside because the suit itself provides no warmth. I used a heavy fleece layer during my 2018 trips to colder regions. You must manage the air volume inside the suit constantly.

Air moves into the suit through an inflation valve. It leaves via an exhaust valve when you ascend or move. If you do not vent air, your buoyancy increases rapidly as you rise. I once felt my buoyancy spike at 12 m because I forgot to open my exhaust valve. This can lead to an uncontrolled ascent.

Control is everything. You must balance gas volume with depth changes.

Why it matters for safety

Thermal protection is a non-negotiable safety requirement in cold water. You will need this gear for diving in places like Japan or the colder parts of the Baltic Sea. Without proper insulation, you will freeze quickly. Hypothermia can impair your decision-making skills within 20 minutes of exposure.

The suit also affects your buoyancy profile significantly. As you descend to 30 m, the water pressure compresses the air inside. You must add air to stay at your target depth. If you neglect this, you will struggle to maintain trim. This physical effort drains your energy and oxygen supply.

Stay warm to stay focused.

Common mistakes to avoid

A common mistake is not checking your seals before every dive. Always inspect the latex or silicone for small cracks. If a seal fails at 25 m, you will get wet fast. Water enters the suit under pressure and cools your skin instantly. This creates a massive thermal shock.

Maintenance is often neglected by busy divers. Keep your inflation valve clear of sand and salt. I saw a diver struggle because silt blocked his valve during a 45 minute dive. A jammed valve prevents you from adding air or venting it. This makes buoyancy control almost impossible in deep water.

Check your equipment twice.

Connection to buoyancy and gas

Drysuit diving is closely linked to buoyancy control and gas management. The suit adds a massive amount of volume to your profile. You cannot rely on your BCD alone for stability. Because the suit holds air, you must use your lungs and valves to fine-tune your position.

Gas density also changes how you breathe at depth. While the suit keeps you dry, it does not change your nitrogen absorption. You still follow standard decompression tables or dive computers. A drysuit allows longer bottom times in cold water by preventing heat loss. This is why professionals use them for technical exploration.

Buy a high-quality thermometer to monitor your core temperature during every dive.