Dry Suit Diving: Buoyancy and Emergency Procedures

At 18 metres his feet lifted and his head dropped. He had been adding air to the dry suit on descent — the same reflex that works in a wetsuit BCD — and now a bubble the size of a football sat at his shoulders while his legs pointed at the surface. He finned hard, lost his reg, and shot upward from 14 metres. The squeeze on his dry gloves during the rapid ascent left his fingers purple for an hour.

Dry suit diving is not "wetsuit diving with more warmth." The suit is a second buoyancy device wrapped around your body, with inflation and dump systems that behave differently from a BCD. This guide covers suit inflation discipline, dump valve sequencing, feet-first ascent risk, squeeze prevention, and emergency procedures — without repeating wetsuit compression physics from the buoyancy article.

1. Dry Suit vs Wetsuit: Different Buoyancy Physics

A wetsuit compresses with depth, reducing buoyancy — you add air to your BCD to compensate. A dry suit traps a gas space around your entire body. That gas compresses on descent and must be replaced via the suit inflator, or you get a squeeze. On ascent it expands and must be vented via dump valves, or you get an uncontrolled feet-first rise.

(For general Archimedes/BCD/wetsuit compression principles, see the Buoyancy Control guide — this article covers dry-suit-specific control only.)

2. Inflation: The Suit Inflator and Gas Choice

The dry suit inflator connects to your regulator (usually a low-pressure port) or a dedicated pony bottle. Short bursts — not continuous flow — maintain suit volume without over-inflation.

Undergarment thickness changes the gas volume needed. A thick undersuit in cold water requires more suit gas — plan weighting accordingly in a pool or shallow check dive, not on a 30 m wreck.

3. Dump Valves: Shoulder and Cuff

Most dry suits have an automatic shoulder dump (set to vent at a given suit pressure) and a cuff dump operated by raising the arm. On ascent, vent before the expanding suit lifts you.

Ascent sequence:

1. Begin venting at 5–6 m or when you feel positive suit buoyancy
2. Raise left arm (cuff dump) while holding depth briefly
3. Fine-tune with shoulder dump setting — pre-dive adjust for expected depth
4. BCD vent handles remaining lift at the surface

4. Feet-First Ascent: The Primary Dry Suit Emergency

When excess suit gas migrates to the feet in a head-down attitude, Boyle's Law takes over: expanding gas accelerates a feet-first surface shot. This is the signature dry suit accident — distinct from BCD runaway because the lift is distributed along the legs.

5. Squeeze: Wrists, Neck, and Valves

Suit squeeze occurs when external water pressure exceeds internal suit pressure. It is painful, can cause bruising, and signals you failed to add gas on descent.

| Site | Cause | Prevention | |---|---|---| | Wrist seals | No suit gas; tight seals | Puff suit gas before deep descent; check seal size | | Neck seal | Head-down + no gas | Maintain volume; avoid extreme head-down trim | | Dry gloves | Insufficient gas in gloves | Equalise gloves with small bursts; avoid cotton liners |

A torn neck seal at depth is a flooding emergency — abort the dive, ascend controlled, signal buddy immediately.

6. Training and When to Get Certified

Dry suit diving requires a specialty course (PADI Dry Suit, SSI Dry Suit Diving, etc.) covering:

• Pool/confined water inflation and dump drills
• Weighting with undergarments
• Emergency procedures including feet-first ascent recovery
• Repair and seal maintenance

Do not rent a dry suit for a cold-water holiday without training and at least one supervised checkout dive.

7. The ScubaProof Filter: Dry Suit Operations

Safety, Gear, Staff Conduct, Oxygen Readiness, and Trust Score on ScubaProof surface operators who maintain dry suit kit and enforce training prerequisites.

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