system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do nuclear missile submarines receive orders from the president to launch a nuke while underwater?
gpt
When deep, an ELF signal can be used to tell them to come up for further info.  Extremely Low Frequency signals are very constrained, so it would take a long time to send/receive a more detailed message.  But once they come up to a shallower depth, they can deploy a floating wire antenna that floats on or near the surface, and can get much higher-bandwidth signals for more details.  Of course, they could also surface, but with the floating wire antenna they don't have to.