[sulam]

There are several circumstances where submarines don't actually use their sonar. They have it, but a submarine that is pinging is easily identified / tracked.

The underlying question is why they were in an area that hadn't been adequately mapped.

[dylan604]

When evading, sometimes you have to leave the safe zone. OpFor will probably be familiar with safe operating areas and limit search zones. Would a USS Captain risk the boat by leaving uncharted areas to avoid detection? Just an idea of why.