Can you survive a tsunami?

A tsunami is not a breaking wave but a fast-moving surge of water that keeps coming, and the danger is as much what it carries as the water itself — vehicles, timber, boats and debris. Only about 30 centimetres of fast-moving water is enough to sweep an adult off their feet, and a metre will move a car. In deep ocean a tsunami travels at jet-aircraft speed and is barely noticeable; it slows and piles up as it reaches shallow water. The natural warning for a locally generated tsunami is the earthquake itself, or the sea withdrawing unusually far, and in those cases the wave may arrive within minutes, so the instruction is to move without waiting for an official alert. Vertical evacuation into a substantial multi-storey concrete building is the fallback where high ground is not reachable, and later waves are often larger than the first, so returning early is a common cause of death.

What changes the figure

• Strong shaking near the coast is itself the warning; do not wait for an alert
• Inland and uphill beats any other action; a few hundred metres of elevation change is decisive
• The first wave is often not the largest, and the sequence can continue for hours

Physiology, not instruction. Every figure here is a population range under particular conditions, and individual variation is large — temperature, exertion, fitness and health move all of them substantially. Nothing on this page is medical advice.

Situations

• Can you survive a plane crash? Usually — across all US airline accidents studied, more than 95 per cent of occupants survived.
• How long do you have to escape a sinking car? Usually 30 seconds to a couple of minutes of floating — and the window is the way out, not the door.
• Can quicksand pull you under? No. Quicksand is roughly twice as dense as a human body, so you float — you sink to about waist depth and stop.
• How far from a nuclear blast do you have to be to survive? It scales with yield: for a one-megaton airburst, survival is unlikely within about 5 km and likely beyond about 10-12 km.
• How long can you survive in a hot car? Under an hour on a warm day for a child — the interior gains about 20 °C in the first ten minutes.
• How long does it take to drown? Under a minute to lose consciousness — and it is almost silent, which is why so many drownings happen in sight of others.
• What happens if a lift cable snaps? Essentially nothing — lifts hang from multiple ropes and have a speed-triggered brake that grips the rails.
• What height can you survive falling from? Survival is common below about 6 metres and rare above 20 — but people have survived falls from thousands.
• How likely are you to survive a shark attack? Very likely — of roughly 60 to 80 unprovoked bites worldwide each year, fewer than ten are fatal.
• What happens if you fall into lava? You would not sink — lava is about three times denser than a body — but you would not survive the heat either.
• What should you do if you are caught in a rip current? Rips pull you out, not under. Swim parallel to the beach until you are out of the flow, then come in.
• Could you survive inside a whale? You cannot be swallowed by almost any whale — their throats are too narrow — and a stomach offers no air.
• How long do you have to escape a burning house? Around three minutes from the alarm sounding in a modern furnished home.
• How long can you survive in a sealed container? Carbon dioxide becomes dangerous long before oxygen runs out — a few hours in a cubic metre of air.