Yes, 300 meters is significantly better, and "deeper is almost always better" is a core principle of blue water submarine stealth.
While 200 meters is the rule of thumb to get below the "sunlight zone" and the permanent thermocline, diving to 300 meters (or deeper) provides three critical advantages.
1. Increased Protection from Non-Acoustic Detection
This is the most significant benefit. The "footprints" a submarine leaves on the surface become exponentially fainter with every meter of depth.
• Thermal Scar: At 300 meters, the hot water from the reactor has much farther to travel, mixing and cooling almost completely before it can ever reach the surface. This makes the sub nearly invisible to satellite infrared sensors.
• Surface Wake (Bernoulli Hump): The surface disturbance a sub creates shrinks rapidly with depth. A wake that might be detectable at 150-200 meters is almost certainly non-existent or lost in the background "noise" of ocean waves when the sub is at 300 meters.
2. More Tactical Freedom (Speed = Stealth)
The biggest enemy of a sub's quietness is its own propeller.
• What is Cavitation? At high speeds or shallow depths, the propeller's spinning blades create a low-pressure zone that literally boils the water, forming tiny, noisy bubbles. This "cavitation" is incredibly loud and a dead giveaway on enemy sonar.
• The Depth Solution: The deeper a submarine goes, the greater the surrounding water pressure. This intense pressure makes it much harder for those bubbles to form.
• The 300m Advantage: At 300 meters, the ambient pressure is enormous, allowing a commander to spin the propeller much faster—and thus move the submarine faster—before cavitation ever begins. The sub can "run quiet" at a much higher tactical speed than it could at 200 meters.
3. A Larger "Playing Field"
In anti-submarine warfare, the ocean is a 3D battlespace. More depth means more room to maneuver.
• Evading Torpedoes: A torpedo hunting a sub has a "search cone." The more vertical water the sub has to work with, the easier it is to "out-fly" the torpedo by diving or climbing.
• Hiding in Deeper Layers: The ocean isn't just one layer. There are often multiple, deeper acoustic layers (sometimes called shadow zones) below the main thermocline. A 300-meter (or deeper) capability gives the captain more options to find the absolute quietest, most hidden part of the ocean.
In short, 200 meters gets you "off the grid." 300 meters lets you move around on that grid, quickly and invisibly, while also erasing your tracks from satellite surveillance.
