Increasing the light factor makes it more difficult, and I ~think~ the surface factor larger also... maybe? I determines the surface area of what the enemy has to "see" of your boat for the set time period for them to "detect" your sub...
Stock:
[Visual]
Detection time=0.5 ;[s] min detection time.
Sensitivity=0.1 ;(0..1) min detection threshold double detection time.
Fog factor=1.0 ;[>=0]
Light factor=2.5 ;[>=0]
Waves factor=4.0 ;[>=0]
Enemy surface factor=50 ;[m2]
Enemy speed factor=25 ;[kt]
Thermal Layer Signal Attenuation=1.0
Adjusting the AI - cliff notes version
From Ducimus, but there are others, and different details, but I cannot find the others as easily...