It's a scenario¹ many of us daydream² about during a heat wave while stuck in a badly ventilated office or on a stuffy³ commute⁴. Being able to cool down by plunging⁵ into a cold lake or have a dip in the sea sounds pretty blissful when temperatures peak at 31.9C.

大热天被困在通风不好的办公室或闷热的交通工具中时，我们都会幻想这样的场景：当气温高达31.9度时，能够跳到冰凉的河水中或在海中畅游降暑。

But while this may sound fun and refreshing⁶, it can actually be incredibly dangerous - deadly even. This is because at the root of large number of drownings is cold water shock. A condition which is rarely discussed, cold water shock can trigger a deadly heart attack. You may not think anything of having a refreshing swim in the cold water, but with the average temperature of the sea off UK shores between 10 to 15C, the RNLI warn this is in fact cold enough to cause cold water shock.

虽然这听起来令人身心舒畅，但实际上却非常危险--甚至会致命。这是因为大量溺水事件的根本原因在于冷水冲击。很少有人谈论这一情况，但冷水冲击可能会引发致命的心脏病发作。也许，你并没有打算在冰冷的河中游泳，但英国海岸海水的平均温度为10至15度，英国皇家全国救生艇协会警告称，这种温度足以导致冷水冲击。

Professor Mike Tipton, author of the book Essentials of Sea Survival, has said: "If you are lucky enough to survive long enough to die of hypothermia, you have done very well. Most die in the first minute of immersion⁷." "It's cold water shock that tends to kill people around our shores," the RNLI warns on their website.

海上生存要领》（Essentials of Sea Survival）一书的作者迈克·提普顿教授说道："如果你足够幸运，能长时间在低体温的境况下存活，那你就已经很棒了。大多数人在浸下去的第一分钟就没命了。""在岸边游泳时，导致人们死亡的原因往往是冷水冲击，"英国皇家全国救生艇协会在网站上警告称。

What happens to your body when you jump into cold water? Cold water will put your body through a number of physiological⁸ responses. The first is one the considerable lowering of your skin's temperature, which being one of the "most profound stimuli⁹ the body can encounter" is a potentially a big strain on your body's resources.

跳入冷水中你的身体会发生何种变化？冷水会让你的身体历经多种生理反应。首先就是皮肤温度大幅度降低，这是"身体能遇到的最大刺激"。于身体而言，这可能是一个巨大的压力。

The RNLI continues: "The responses tend to be short lived, but threaten survival." You'll find your blood vessels¹⁰ start narrow, reducing the amount of blood which can circulate. "The heart then has to work harder and blood pressure increases," the RNLI explains.

英国皇家全国救生艇协会继续道："身体的反应往往是短时间的，但却会威胁你的生命。"你的血管会开始变窄、减少血液循环。"之后，心脏运作更为困难，血压升高，"英国皇家全国救生艇协会解释道。

"At the same time there is a 'gasp¹¹' response, which can result in water being breathed in rather than air. The breathing rate changes dramatically, it can increase by as much as tenfold. "

"同时，还会出现'喘息'反应，导致人们吸入水而非空气。呼吸速率急剧变化，甚至能加快10倍。"