A few minutes in this hot spring
would leave you feeling refreshed.
But what would happen if you camped out
in this foul-smelling pool for 24 hours?
Humans have used hot springs
for thousands of years to relax
and treat medical conditions.
These waters shoot up
from below the Earth's surface,
heated by churning magma.
And the water brings sulfuric compounds
that create that fragrant aroma.
All that ancient hot rock below
boils these waters
to temperatures around 50 °C (122 °F).
I know it smells,
but it feels great.
In Japan, authorities recommend
you only stay in some hot springs
for 40 minutes at the most.
But what would happen if you
fell asleep in this hot pot?
This hot spring
looks so warm and inviting.
Why could it be so dangerous?
Well, what lies beneath the waters
could be fatal.
But we'll get back to that.
While these waters can feel soothing,
the temperature
might reach near 100 °C (212 °F)
if this spring becomes superheated.
If it got to just the right temperature,
this highly acidic water
could burn your skin within 10 minutes.
So a whole day
might cook you like a hard-boiled egg.
But if this water stayed at medium heat,
could soaking in it replace your workout?
A 2015 study in Finland found that
one hour in a hot spring could burn off
as many calories as a 30-minute walk.
Unfortunately, the sample group
only included men.
OK. Don't get too excited.
Your body would be working overtime
to deal with the excess heat.
That means you'd be using more energy
to stay at a normal temperature.
As the hot springs simmer you,
the real test of your body's limits
would begin.
You need to maintain
an internal temperature of 37 °C (98.6 °F)
to keep your body systems working.
But the danger starts if your temperature
rises just a few degrees.
You could get hyperthermia,
a dangerous condition that could have
consequences long after you dry off.
You could experience heatstroke
or even heat edema, which
would make your hands and feet swell.
You may not survive unless you get out
and into a cold bath right away.
And even if you cool down,
there's a chance that you could experience
organ and neurological dysfunction
within a year.
During this bath,
your heart rate would increase,
and you would start feeling dizzy.
Try to stay awake because
you might faint and slip under the water.
And keep your nose plugged because
deadly microbes might lurk
beneath this hot water.
While most living organisms
may not stand a chance in this heat,
the Naegleria fowleri amoeba
thrives in hot springs.
This microscopic threat
could travel up your nose to your brain.
And within a week
after you feel symptoms like fever,
nausea and a stiff neck,
you could be dead.
But while you're in the hot spring,
you'd keep sweating and get dehydrated.
You'd lose body fluids
at about 1.5 L (50 oz) or more per hour.
As the electrolytes and minerals
left your body,
your arms, legs and abs
could start cramping,
sending you into a world of hurt.
When you lose control of your muscles,
this hot spring
could become a giant toilet.
OK. Seriously, let me out now.
Now it's just a matter of time
before your blood vessels leak.
This could cause violent hemorrhaging
and make you puke blood.
And your intestines
would release toxins into your bloodstream.
Your organs would swell up
like steamed sausages,
and that includes your brain.
If you managed to
crawl out of this cesspool,
your body would be a wreck.
And that's if things go well.
After the 1995 heatwave in Chicago,
28% of heatstroke survivors
died within a year from complications.
And 51% were left with
permanent organ dysfunction
and brain damage.
The next time you visit
one of these natural wonders,
enjoy soaking.
But remember to stay hydrated,
watch your time
and keep your head above water.
But what if you wanted to try this
from the comfort of your own home?
What if
you stayed in a bathtub for a week?
Grab your rubber duckie
because that's a story
for another WHAT IF.