High seas tactics...?

[Bulkhead]

What is your approach to attack a ship or convoi in ruff seas?
I am talking about manual targeting and high realism.

I just wanna hear the different opinions/ways to do this.

I find it very hard to do for more than one reason.
Difficult to make a distanse to the target because it goes up and down in the waves.
Water that washes over the periscope and causes me to loose the lock-on-target.

I have given up and dont bother trying , i just follow under surface or at radar distance.

Any tips and tricks?