A likely source of bottles with messages would be an oceanographic
institution with a drift-bottle program. There may be some such in Germany.
If I were looking for such a program in the US, I would start by asking
George Hemingway of Scripps Institution -
ghemingway@ucsd.edu
Bill R.
W. Riedel
Scripps Institution of Oceanography
UCSD
La Jolla, CA 92093-0220
wriedel@ucsd.edu
phone (619) 534-4386
fax (619) 534-0784
. . . . May the Force be with you . . . .