a live text stream of messages originally transmitted via navtex or AIS which sounds like computer noise on a radio but can be decoded by software applications or specially designed equipment. Navtex is used by nautical entities to track things like hazards or pirates or weather conditions
for example:
ZCZC MA72 041135 UTC JAN = WZ 024 ENGLAND, EAST COAST. THAMES ESTUARY. KENTISH KNOCK SOUTHWARDS. UNEXPLODED ORDNANCE MARKED BY PINK BUOY REPORTED 51-34.04N 001-36.95E. CANCEL WZ 1210 (GA01) (MA37).+ NNNN