Stay out of the Channel
However, if you feel that you must at least have a go at it, then I suggest the following.
Hug the French Coast as much as possible.
Submerge during the day.
Surface at night & do not use TC. (The Elco's are buggers to spot & they call friends)
Always Silent Running
No faster than 2kts submerged.
Surface, travel as fast as possible.
Pray for Fog/Bad Weather.
If you get through you are lucky.
(oh, p.s. Look out for mines
)
Edit - Gib is easy compared to the Channel.
