What are negative impacts of submarines have on life?

Contrary to activist groups claims, Navy ships and submarines rarely use active sonar. Active sonar produces sound, and lots of it, that gives away a vessel's position to other enemy ships and submarines.

The biggest impact that subs have on marine life, is that they pump waste overboard. Sewage is very popular with schools of fish, because the think it tastes great. Oil being pumped overboard is bad. The crews make every effort not to pump oily waste overboard. There are collection tanks just for oily water and such.