n00b sonar query

[coolts]

Guys
I’ve been out of the SH loop since SH3 and can’t remember what the difference between the sonar contact lines on the map are. In SH5 you get black and blue lines pointing towards contacts. I am surfaced so was assuming blue meant visual and black sonar. I could test by submerging but I am at work.
Tried searching but the search function on this site is a bit……special.
Cheers