We have detected an underwater contact.

If you have been following instructions, this will be a passive sonar contact detected by the SQS-26CX hull sonar.

Note that there is an area of ambiguity around the contact, and that we do not have depth information for the contact. Since passive sonar uses target motion analysis to deduce the position of contacts it is normal to have some ambiguity about the position--the noisier the contact and the better the sonar sensor, the less ambiguity will exist and vice-versa.

Now switch on active sonar by checking the 'active' box next to the entry for the SQS-26CX in the sensors dialog (F9) or by changing unit EMCON settings in the right hand side status bar. Note that the area of ambiguity disappears after a few seconds and we now have a firm position for the contact.

As mentioned earlier, the contact is an old obsolete submarine that has had its weapons and sensors removed--it's harmless. Close in until you have a type classification on the contact. Try different speeds and turning the active sonar on and off to see some of the factors that determine whether a contact is able to be tracked.