Why is going down in a submarine such a big deal?

I've sailed the seven seas.

I flew helicopters in the Army.

I've jumped out of planes.

Flown helicopters, fixed wing planes, and gliders.

And done a thousand other things. . .

But being on a submarine is just not on my 'bucket list.

We humans live with "Atmospheric Pressure" all the time. As you go up in an Airplane that pressure is gradually reduced. So Commercial jets "pressurize" the cabin so that you are comfortable. However Water is much different than air. It doesn't compress. It weights 32 pounds per cubic foot. So as you submerge the pressure on your body would rapidly increase. You might have noticed this when swimming. The deeper you go the higher the pressure.

Once you reach a depth of a few hundred feet, you need to be inside something to protect you from these pressures. Submarines are built to do just that. The inside pressure remains at basically sea level, while the hull takes the pressure of the water. Most subs operate in relatively shallow depths. Often less than 1000 ft. deep. Even so the pressures at that depth are very large. Therefore even a minor problem can sink the sub.

The pressure at 1000 ft. deep is 445 pounds per square inch. Only a few submarines venture to depths of 4000 feet. Beyond that you need diving bells and deep sea submersibles. Which for some strange reason are not considered submarines.

At 5000 ft the weight of the water is about 2500 pounds per Sq. inch That's about 150 tons per sq. ft.

Because you don't come back up looking like a flattened bug! If you are a flattened bug, you'll never know it should the Submarine hull collaspe. Since there are no windows, you can't even tell the world good bye.

Submarines are complex and expensive to build safely. Military ones don't have windows and they usually don't let civilians on board, and research ones don't hold many people at one time. So very few people have actually done it.

There are many reasons why a "dive" is announced...too many to list. But s summary answer would be "safety" to crew & vessel.

Because sometimes you don't come back up.

WHY DONT YOU TRY NOT SEEING DAYLIGHT, FOR SEVERAL DAYS.......................AT A TIME