Survival at sea depends on staying warm, staying afloat, and being found quickly. Cold ocean water can remove body heat much faster than cold air, so a person in the water can lose strength and judgment within minutes. Immersion suits, life rafts, and emergency radio beacons are designed to slow heat loss, reduce drowning risk, and guide rescuers to the correct location.
These tools are used on ships, submarines, fishing vessels, and offshore platforms because rescue may take hours or even days.
Key Facts
- Water conducts heat away from the body about 25 times faster than air at the same temperature.
- Heat transfer by conduction increases when the temperature difference is larger: rate is proportional to ΔT.
- Buoyant force equals the weight of displaced water: F_b = ρ_water V_displaced g.
- An object floats when its average density is less than the density of seawater.
- EPIRBs transmit emergency signals, often near 406 MHz, to satellites that relay a distress location to rescuers.
- Survival priority at sea can be summarized as float, insulate, signal, and stay together.
Vocabulary
- Immersion suit
- A waterproof, insulated survival suit that reduces heat loss and helps a person stay afloat in cold water.
- Life raft
- An inflatable emergency craft that keeps survivors out of the water and provides shelter while they wait for rescue.
- EPIRB
- An Emergency Position Indicating Radio Beacon that sends a distress signal and location information to rescue systems.
- Hypothermia
- A dangerous drop in core body temperature that can reduce movement, thinking ability, and heart function.
- Buoyancy
- The upward force from a fluid that can support an object or person in water.
Common Mistakes to Avoid
- Thinking an immersion suit makes someone completely safe. It slows heat loss and improves flotation, but the survivor still needs to get into a raft and signal for rescue.
- Opening or entering a life raft without securing it to the vessel or survivors. Wind, waves, and current can carry an unsecured raft away very quickly.
- Assuming calm behavior is less important than equipment. Panic wastes energy, increases breathing problems, and can prevent correct use of suits, rafts, and beacons.
- Forgetting that an EPIRB must be activated and have a clear path for its signal. A beacon that is not turned on, is shielded by metal, or is left below deck may not alert rescuers effectively.
Practice Questions
- 1 A survivor in 5 °C seawater wears an immersion suit that reduces heat loss by 80 percent compared with ordinary clothing. If ordinary clothing would allow 500 W of heat loss, what is the heat loss while wearing the suit?
- 2 A life raft displaces 0.90 m3 of seawater when loaded. Using ρ_water = 1025 kg/m3 and g = 9.8 m/s2, calculate the buoyant force on the raft.
- 3 Explain why getting into a life raft is usually safer than remaining in the water, even if the survivor is wearing an immersion suit.