---
name: Undersea Cables
slug: undersea-cables
type: physical_infrastructure
status: running
version: 4.2.1
released: 1858-08-05
maintainer: consortium of telecom operators, hyperscalers, and nervous governments
dependencies:
  - ocean floor
  - repeater stations
  - landing stations
  - international maritime law
  - a ship that knows what it is doing
license: Proprietary (per cable, per consortium)
tags:
  - infrastructure
  - internet
  - telecommunications
  - hidden systems
  - load-bearing obscurity
---

Undersea Cables

What it actually is

The actual internet, lying on the seafloor in a tube roughly the diameter of a garden hose, carrying approximately 95% of all international data traffic while everyone argues about satellites.

How it works

A cable is laid from a purpose-built ship across thousands of kilometers of ocean floor. Inside: fiber optic strands that transmit data as pulses of light. Every 50 to 150 kilometers, a submerged repeater amplifies the signal using power delivered down the cable itself from the shore.

The cable is armored near coastlines, where anchors, trawlers, and bored sea life constitute genuine threat vectors. In deep water, where nothing can reach it, the cable is left relatively thin. This is either elegant engineering or aggressive optimism, depending on your mood.

Landing stations at each end connect the ocean segment to terrestrial networks. These buildings, often unmarked, on beaches in places like Bude or Fujairah, are some of the most consequential structures on Earth. They look like small offices. They contain the entire conversation.

Features

Latency measured in milliseconds across oceans (physics is doing its best)
Bandwidth measured in terabits per second per cable
Passive enough to be forgotten until they break
Surprisingly repairable, via the same ships that lay them
Geopolitically interesting in ways their maintainers would prefer they were not

Known bugs

Bug	Frequency	Root cause
Anchor strike	Common	Fishermen, merchant vessels, indifference
Shark bite	Rare but documented	sharks find the electromagnetic field compelling
Submarine fault rupture	Uncommon	tectonic plates doing their thing
State actor interference	Classified	Disputed
Cable overboard by accident during repair	Once (hopefully)	See: 2022 Tonga outage

"We had no idea that sentence traveled through the bottom of the Atlantic Ocean." — most users, if they thought about it

Configuration

depth_range: 0m to 8,000m
fiber_pairs: 4 to 16 per cable
design_life: 25 years
actual_life: longer, worryingly
ownership_model: consortium (shared risk, shared blame)
geopolitical_status: technically neutral, actually not

Edge cases

Cables do not respect territorial waters neatly. Jurisdiction becomes creative at depth.
When a single cable connects a small island nation to the rest of the internet, its failure is a national emergency.
Several cables pass through the Red Sea in a cluster, creating a single point of failure for a significant portion of global traffic. This is known. It remains the case.
surveillance of cable traffic at landing stations is legal in many jurisdictions and optional in approximately zero of them.

Changelog

1858: First transatlantic cable. Worked for three weeks. Celebrated prematurely.
1956: First transatlantic telephone cable. More durable.
1988: First fiber optic undersea cable. Everything accelerates.
2010s: hyperscalers begin funding their own private cables. The map gets complicated.
Present: Over 400 active cables. Still mostly invisible. Still load-bearing.

drafting spec…