Depends on the type of vessel, if you stop on the way, how many times and how long for. If you mean by cruise liner then I would check with a travel agent directly as the number of stops will vary.
6 weeks
approx 72 days
45 days
You can't sail from London to Cologne.
how long does it take to sail from Pakistan to England
Try looking at a map and you'll see that Johannesburg is about 500 miles from the nearest coast!!
a long time
a long time
3 hours about
4 days
About three weeks.
a long time