One way to make it more realistic is to move in a position a little of the side of the estimated convoy course at the edge of the visibility.
When it is dark enough , then make a turn towards the convoy and start your attack run.
Real tactics advised the so called "dog-curve " for a surface attack.
As GWX makes it very difficult to start the attack unseen, I ususally dive at half the visibility and make my final run submerged against the outer lanes of a convoy.
....But sometimes I am bold enough to stay on the surface ...

and then it gets realy exciting
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SH3 battle capability upgrades: GWX2.0, JSGME2.0, SH3Commander 2.7, SH3Gen 0.8.2, TorpDamageMod 2.0, OLC GUI 1.1.5
Awaiting combat readiness for GWX2.0: SH4 effetcs for SH3, SH3Weather 1.5
Following development of:
www.subwolves.com
Realism: 90%