Dual military/civilian purposes

If the submarine is tracked, the element of surprise is lost, and the offensive nature of the submarine is redundant.

http://en.wikipedia.org/wiki/List_of_submarine_incidents_since_2000#USS_Montpelier_collision_with_USS_San_Jacinto

In today's more peaceful, less violent world, what would you do if your submarine were discovered when the effective nature of the lethal submarine is to kill first or lose the element of surprise?

http://en.wikipedia.org/wiki/Talk%3AEhime_Maru_and_USS_Greeneville_collision#Formatted_list

This is why,
Bermuda Triangle.

http://en.wikipedia.org/wiki/Soviet_submarine_K-219

K-219 was involved in what has become one of the most controversial submarine incidents in the Cold War.

 The MFV Bugaled Breizh is a French trawler from Loctudy, Finistère, whose sinking with all hands on January 15, 2004 remains unresolved. While it appears likely that the ship was pulled under by a submarine, a specific submarine could not be...

http://en.wikipedia.org/wiki/Bugaled_Breizh#Submarine_involvement_.22likely.22

Does dragging surface ships via shipping nets disrupt sonar to hide submarines?

The dual use of ocean based oil rigs. Like underwater forest protection from sound based radar aka sonar. And submarine depots.

http://articles.latimes.com/1989-10-26/local/me-648_1_oil-rigs

"Oil rigs and noise from drilling would interfere with a variety of exercises now conducted, including sea-skimming missile and acoustic instrumentation tests, according to the report issued by Capt. J. B. Hinkle, director of Navy Programs, in Washington."

...Googling 'Archerfish 1981 rig' in the search for the particulars of the USS Archerfish colliding with an oil rig is not findable. NSA..

Did you know lasers are ineffective in fog and rain?

One solution to global warming serves as a dual purpose to counter directed energy weapons and reduce drought. protects planes from flak, deters remote sensing and targeteers, makes parachute landings unpredictable, etc...

http://en.m.wikipedia.org/wiki/Cloud_seeding

First person shooters increasingly prepares us to remote control battlefield robots. If you call that desensitizing, I say it eliminates the risk of the operator from a short lived life.

http://www.fas.org/irp/agency/army/mipb/1997-1/merkle.htm

"The Outer-Space Treaty of 1967, since ratified by the members of the United Nations, explicitly states that treaty partners not place any objects carrying nuclear weapons in Earth's orbit great idea, in principle. The trouble is, the treaty does not oblige any nation to allow others to inspect the cargo they send into space."

...smuggling camouflaged weapons into space.

http://en.m.wikipedia.org/wiki/2009_satellite_collision

The 2009 satellite collision was the first accidental hypervelocity collision between two intact artificial satellites in low Earth orbit.[1] It occurred on February 10, 2009, 16:56 UTC, when Iridium 33 and Kosmos-2251 collided [2][3][4] at a speed of...

Space weaponizing capability demonstration, by Russia; the 2009 Satellite Collision (Wikipedia)

http://www.world-nuclear.org/info/Non-Power-Nuclear-Applications/Industry/Nuclear-Desalination/;

"The main opportunities for nuclear plants have been identified as the 80-100,000 m³/day and 200-500,000 m³/day ranges. US Navy nuclear powered aircraft carriers reportedly desalinate 1500 m3/d each for use onboard."