Ways Submarines Hide There Identity

The ways submarines hide their presence or identity include:

•  Sail in noisy shipping lanes. 

•   Move at night if in a seaspace or near shore where you might be detected. It is harder at night for a poorly equipped non-state enemy or other forces to see a snorkel, periscope or submarine at night. But beware of radar, light intensification or thermal imaging sensors belonging to a better equipped enemy.

•   There is typically less shipping and other sea traffic movements at night, making it easier for a submarine to move at its own optimal pace eg. more slowly and quietly than higher daytime shipping movements would allow.

•   Be "propelled" by tides if possible. Saves on battery output if you are an SSK. UUVs also take note.  

•   If tides are a problem adjust speed at the speed of the tide so as to "hover" eg. if off-shore surveiling an enemy coast with your periscope or listening to faint, short range, emissions from on-shore bugs/microphones. Also UUVs might do this at much lower cost - no risk to human life. 

•   Use a "stalking horse." A submarine may follow a larger, more easily detected ship using the ship's noise to mask its own.

More at https://www.quora.com/How-do-nuclear-submarines-leave-port-undetected

Here is a touching tale from a "Thomas Hathaway, Tailor, Costumer, Prop and Model Maker of 30 Years":

“I was born on a sub and raised by the crew. [...employed as a cabin boy and drummer.] When I was old enough I enlisted and became a part of the crew. When my first enlistment was over, I decided to leave the only life I knew. My family loaded me on to the mail buoy and said good bye to that life forever.”

Heartening stuff!