Why does submarine first submerge would be 150 ft?

Question

I've been watching couple submarine movies(Crimson Tide is one of them, great movie btw), and i realized everytime, the submarine's captain always tell the diving officer to submerge the ship to the depth of 150ft?

Answer 1

Sonar efficiency is greatly increased once the submarine submerges. Sonar acts as the "eyes" of the submarine when operating submerged. Before proceeding to deeper depths the caption will want to verify that there are no contacts along their intended path of travel. The other answers are also partially correct as water tight integrity is tested as the dive begins. As the submarine submerges, the crew makes a checks for leaks. Such a shallow depth however is not much of a test for hull strength.

There are two reasons why sonar operates better submerged:
1. There is a thermal layer just below the surface. This is where the temperature of the water changes quickly with depth. These thermal layers tend to reflect sound. A submerged contact operating below the layer is harder to detect when the submarine is above the layer.
2. Operating on the surface creates noise. This self-noise is also received by the submarines sonar and can mask fainter sounds.

Answer 2

This is done to test the submarines hull for strength and air tightness. After that is done the hull will compress and expand as necessary for the depths that the submarine will operate.

Answer 3

This is an energy efficient layer the sub can maneuver in and is deep enough to avoid shipping traffic but shallow enough to pop up if there is an emergency.

A nice cruising depth.

Answer 4

In Navy habits change very, very hard....