Haha, in Germany he's definitely not known as "the man from Das Boot". As Wikipedia says, "His fifth album 4630 Bochum (1984) and his 20th album Mensch (Human) (2002) are the best-selling German-language records of all time"
http://en.wikipedia.org/wiki/Herbert_Gr%C3%B6nemeyer
So he's a popular "adult contemporary" singer, I suppose. Here's the sort of stuff he does: