Very low and extremely low frequency transmissions penetrate seawater but offer limited bandwidth and generally require huge shore transmitters. Submarines can report through delayed expendable communication buoys, reducing the connection between a transmission and the boat's current position. World War II wolf packs exposed the opposite problem: coordinating dispersed U-boats generated radio traffic that could be analyzed even without reading every encrypted message. A Type XXI boat's underwater performance would not solve that organizational weakness because surfacing or exposing antennas to coordinate a pack would surrender much of its stealth.
Chapter · 1:35:09-1:45:58
Submarine communications sacrifice stealth for coordination
VLF and ELF can send limited one-way orders to submerged boats, while return messages and wolf-pack coordination risk revealing positions.