Cold, choking, bleeding and burns
Cold water shock and hypothermia
Cold shock hits in the first minute. Hypothermia is a falling core temperature and develops later. They are not the same problem.
Water at 15°C and below is cold water. Falling in can make you gasp, breathe in an uncontrolled way, and make the heart work harder. Those first effects pass in less than a minute, so do not try to swim straight away. Float until you can control your breathing, then call for help or swim if you are able. A lifejacket makes that much more likely.
Source: RNLI, Cold water shock
Hypothermia means core temperature has fallen below 35°C. Normal temperature is about 37°C. Shivering, pale or blue-grey skin, slurred speech, slow breathing, and tiredness or confusion are warning signs. It is an emergency. Call 999.
At sea, make the emergency call to HM Coastguard.
Source: NHS, Hypothermia MCA, MGN 623 (M+F) Amendment 1: Telemedical Advice Service (TMAS) for ships at sea
Move the person to shelter. Remove wet clothing and wrap them in a blanket, sleeping bag, or dry towel, with the head covered. If they are fully awake, give a warm non-alcoholic drink and something sugary, such as chocolate.
Source: NHS, Hypothermia
Do not use a hot bath, hot water bottle, or heat lamp. Do not rub their arms, legs, feet, or hands. Do not give alcohol. Stay with them until help arrives.
Resuscitation Council UK's first aid page also lists insulation, shelter from wind, removal of wet clothing, and insulation from the ground.
Source: NHS, Hypothermia Resuscitation Council UK, First Aid Guidelines (2025)
In a hot cabin or a tropical day, heat stroke is the opposite problem: confusion, agitation, seizures, or unresponsiveness in the heat. Move the person into shade, remove excess clothing, and start cooling. If you cannot measure core temperature, keep cooling for 15 minutes or until the neurological symptoms settle, whichever comes first. Cool them before a long transfer.
Source: Resuscitation Council UK, First Aid Guidelines (2025)
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Check your understanding
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1. You fall overboard into cold water and can float. What should you do in the first minute?
2. Which temperature does the NHS use to define hypothermia?
3. A soaked crew member is shivering and confused in the cabin. What should you avoid?
4. Someone is confused and agitated after working on deck in severe heat. What is the priority?