Get your contacts classified and figure out your tactical situation ASAP.
"How deep" isn't as important as who you're up against.
Part of this reply is based more on "real world" than DW, but its still valid. Look at the total picture. If you've got surface contacts, yeah they're on the surface BUT what are they doing? Ships in transit tend to go fast in one direction, they have somewhere they need to be. Skimmers going slow and changing direction a lot are fishing. Maybe for tuna, maybe for YOU.
With subs, again figure out what you're up against and
then look at what they're doing:
Diesel/SSG's- If they're making decent turns, they're transiting. They're also either shallow on the snorkel or surfaced. If they're on the battery, they're looking for something- probably you.
Boomers/SSBN's- Transit deep and slow, patrol deep and slow, run away from trouble deep and slow. Starting to see the pattern? The whole point to a boomer is lost if the other side can find it.
SSGN's- Aircraft Carrier hunters. Transit fast and deep. Go shallow to launch the big missiles and then go deep again. Focus on the Carrier part, SSGN's are designed to hunt very large and fast ships. They more or less need a "wolfpack" to work with, so watch out for picket diesels, helo's, or SSNs.
SSN's- You're more or less on equal footing. How deep an SSN is doesn't matter as much as where you picked them up and which direction they are moving. This is where it pays off to know
who you are tracking. What kind of fish do they carry? How good is their sonar? What tactics do
you need to set up for a successful attack?