Catching up to the enemy

[PurpleCow]

I am playing Cold Waters (no mods installed) and find I have trouble completing the 3rd single mission taking on a surface group. The most modern sub I can command is the Sturgeon class. I find that I can never keep up with the surface group or get within torpedo range. The surface group is just running too fast.

If there is any sort of thermal layer I dive below it and run at 20 knots but as I get closer the surface group detects me. If I drop to 10 knots or less they outrun me.

The Mk 16 torpedo (no wire guidance) can only be launched at under 100 ft depth so I must come near the surface to attack and once I do attack the torpedos are fire and forget with no wires to help guide them.

Any suggestions on how to close into the surface group without giving myself away and having them outrun me?

How did subs of the time (early 1970's keep up with Soviet surface groups?

Thanks all. I love this game!