When a floating submarine submerges, it deliberately goes beneath the surface - which it is designed to do
A submarine is a sea going vessel that is designed to run submerged or on the surface of the sea. Basically, by filling ballast tanks with sea water, the submarine will sink, and by blowing out the sea water from the ballast tanks with compressed air, the submarine will float on the surface.
it's appropriately called the dive alarm.
As a submarine submerges, it is subjected to a high volume of water pressure, which increases the further in depth the submarine goes. They have to be built to be able to withstand this pressure.
A submarine has a variable buoyancy due to it's ballast tanks. When a submarine submerges, it fills it's ballast tanks with water which causes negative buoyancy. When a submarine surfaces, it pumps the water out of the ballast tanks thus giving it positive buoyancy.
Positive Buoyancy. When submarine submerges, it initially uses negative buoyancy to submerge, and then levels out to neutral buoyancy.
A submarine submerges by adjusting its ballast tanks to let in water, making it heavier than the water it displaces, causing it to sink. To resurface, the submarine pumps air into its ballast tanks, displacing the water and causing it to rise to the surface.
it does NOT "sink" - unless by accident or enemy action. It "submerges" - so that it can act stealthily, moving around below the ocean surface so it is very hard to detect.
A submarine can submerge by filling ballast and trimmer tanks with sea water. The additional weight will take the submarine down. To resurface, the submarine will blow the sea water out of the tanks using compressed air. The air in the tanks make the submarine buoyant, so it rises and floats on the surface. Though a stationary submarine can submerge in this way, it usually submerges going forward and using diving plane (fins) to steepen the dive, so getting under the surface faster.
a diver
At very low depths, water pressure becomes exceedingly high. If a submarine submerges below it's depth tolerance, the water pressure outside will exceed the limits of the pressure hull which maintains a normal air pressure for the crew. This will collapse the hull. This is referred to an implosion because the destruction comes from the outside in a crushing manner.
It would not be tied up.
the echo man