Surely many people at least once in their lives wondered why, during a shipwreck, all the unfortunate people jumping overboard simply cannot stay on the water in order to escape a sad fate. After all, swimming, especially "lying on your back" on the water is not so difficult. It's actually not that simple.
The film "Titanic" answers this question very briefly and at the same time eloquently, even though the idea of gaining knowledge and skills from Hollywood films is a frankly dubious undertaking. It should be understood that in the vast majority of cases, the water temperature in the sea or lake is lower than the optimal human body temperature of 36 degrees. And this means that as soon as the body falls into cold water, it first begins to cool down, then freeze, and at the very end - to numb.
And all of the above is happening at an alarming rate. So, a water temperature of 26-30 degrees is considered relatively safe for humans. However, even in this case, a person will lose consciousness in it after 8-12 hours. And this is the best option possible in a ship wreck. All others are much worse.
Note: the average water temperature in the Pacific Ocean is 15 degrees.
Already at a temperature of 19-21 degrees, a person can stay in the water for no more than 40 minutes. Loss of consciousness occurs in 3-7 hours. Death from hypothermia after 8-10 hours. At a water temperature of 16-18 degrees, a person can stay in it for no more than 30 minutes. Loss of consciousness will occur in 2-4 hours, guaranteed death - 6-8 hours.
At a temperature of 13-15 degrees in water, you can stay no more than 20 minutes, after which hypothermia will begin. Loss of consciousness after 2-4 hours, death from cold - after 4-5 hours.
At a temperature of 10-12 degrees, the figures, respectively, are 10 minutes, 0.5-1 hours before losing consciousness and death in less than 1.5 hours. Finally, if the water temperature is about 10 degrees Celsius, then you can stay in it for no more than 3-5 minutes. The person will lose consciousness and die in less than 1 hour.
Finally, do not forget that not everyone knows how to swim. Not all people are psychologically ready for such a struggle for life. Plus, people are prevented from staying on the water by numerous clothes, and at the time of the ship's wreck, everyone who happened to be with him will be pulled under the water by the outgoing streams, which are created by the ship itself at the time of submersion.
Continuing the topic, read about what is a ship's bulb and why the ship needs it.