[dragonwriter]

> Don't submarine use some form of radars to figure what's around then and where are they headed?

No. Radar is basically useless under water (many submarines do have surface search radar available, but that wouldn't help), and while they have sonar it breaks stealth and is usually used tactically, and with a very specific cause, not as a continuous interrogation of the environment.

[jandrese]

Also active sonar deafens nearby sea life. Running around with it on constantly would be an ecological harm.