Survival at sea: cold water immersion, hypothermia and drowning
What this domain tests
Cold water kills in stages, and the exam wants the stages, the timings and the correct response at each. You must also recognise drowning as a breathing problem first, not a circulation problem.
The three stages
- Cold shock (first 1-3 minutes): sudden gasp, hyperventilation and racing heart. The danger is inhaling water. Float, keep the head up and control your breathing; do not thrash or shout.
- Cold incapacitation (roughly 3-30 minutes): hands and limbs stop working, grip is lost and even strong swimmers cannot swim far. This is why you stay with the craft instead of swimming for shore.
- Hypothermia (after about 30 minutes, sooner in icy water): core temperature falls below 35 degrees Celsius. Shivering, then no shivering, confusion, slurred speech, drowsiness and slow pulse. Handle the casualty gently; rough movement can trigger cardiac arrest.
HELP and huddle
- HELP: knees to chest, ankles crossed, arms hugged across the chest, head down, stay still.
- Huddle with three or more survivors, arms around each other, children and injured in the middle.
- Keep clothing on, button up, keep the head clear of the water, never drink seawater or urine.
Worked example
You are in 10 degrees Celsius water, 300 m from shore, wearing a lifejacket. For the first two minutes you float and breathe slowly. Swimming 300 m would take longer than your muscles will last once cold incapacitation sets in, so you adopt HELP, stay with the other survivors and wait for the boat.
Traps
- Swimming to 'keep warm'.
- Drinking alcohol, which speeds heat loss.
- Rubbing or warming the limbs of a hypothermic casualty.
- Giving food or drink to a drowsy survivor.
- Starting compressions before rescue breaths on a drowned casualty.