Undersea Cable Cuts: What an Internet Outage Means for Your Home

Quick answer: Undersea cables carry over 99% of international data. They break often, mostly through accidents with anchors and fishing gear, and in 2025 more than 170 cable repairs were reported worldwide. Recent cuts in the Baltic and Red Seas were mostly absorbed by rerouting, so few households noticed. Even so, it is wise to be ready for an internet or mobile outage: keep a battery or wind-up radio, a paper list of phone numbers, offline maps, a charged power bank and some cash.

Why undersea cables matter

Almost everything you do online that crosses a border travels through fibre-optic cables on the seabed. The International Telecommunication Union (ITU), the UN agency for digital technology, says these cables carry over 99% of international data. Some undersea cables also carry electricity between countries.

Damage is common and usually accidental. The ITU says the main causes are human activity such as fishing and anchoring, followed by natural hazards like earthquakes and underwater landslides. It counted more than 170 cable repairs in 2025, almost four a week. In November 2024, the ITU and the International Cable Protection Committee set up an advisory body to help countries repair cables faster and reduce damage.

Baltic Sea incidents, 2024–2026

The Baltic Sea has seen a run of cable incidents. Some are still under investigation, and in at least one case investigators concluded it was an accident.

C-Lion1, November 2024

On 18 November 2024, the C-Lion1 data cable between Finland and Germany broke east of the Swedish island of Öland. It is the only direct cable link between Finland and western Europe. Its operator, Cinia, said traffic switched to other routes with minimal disruption, and the cable was repaired by 28 November.

Estlink 2 and data cables, December 2024

On 25 December 2024, the tanker Eagle S dragged its anchor about 90 km (55 miles) across the seabed in the Gulf of Finland. It damaged the Estlink 2 power cable between Finland and Estonia and four data cables. The power link carries 650 megawatts. Finland’s grid operator, Fingrid, said the damage did not affect the functioning of Finland’s electricity system. Estlink 2 returned to commercial use on 20 June 2025.

A Helsinki district court first dismissed criminal charges against three of the ship’s officers, saying Finland lacked jurisdiction. In August 2026, the Helsinki Court of Appeal overturned that decision and sent the case back for trial.

Latvia–Sweden cable, January 2025

On 26 January 2025, a data cable between Sweden and Latvia was damaged. Sweden seized the cargo ship Vezhen. On 3 February 2025, a Swedish prosecutor concluded the ship’s anchor had caused the damage by accident: faulty anchor locks, a wave that released the anchor and a crew who failed to notice. It was not sabotage.

New Year’s Eve 2025

On 31 December 2025, Finland detained the cargo ship Fitburg after a telecom cable between Helsinki and Tallinn, owned by Elisa, was damaged. Elisa said its services were not affected because traffic was rerouted. Finnish investigators later said they suspect the ship’s anchor caused the damage.

How Europe is responding

In January 2025, NATO launched Baltic Sentry, using ships, patrol aircraft and naval drones to watch over undersea infrastructure. In February 2025, the European Commission published an Action Plan on Cable Security. It covers four areas: prevention, detection, faster repair and deterrence.

Red Sea cable cuts, 2024 and 2025

In late February 2024, three Red Sea cables (Seacom, AAE-1 and EIG) were damaged off Yemen. The International Cable Protection Committee said the generally accepted cause was the anchor of the cargo ship Rubymar, which had been attacked and later sank. These cables carry about a quarter of the region’s traffic, according to the operator HGC.

In early September 2025, cables including SMW4 and IMEWE were cut in the Red Sea. The AP reported slower internet in countries including India, Pakistan, Saudi Arabia, Kuwait and the United Arab Emirates. Microsoft warned that users in the Middle East might see higher delays. The cause was not immediately clear, and the AP noted that repairs can take weeks because ships must first find the damage.

What an internet or mobile outage means for a household

In the Baltic cases above, operators rerouted traffic and most people noticed nothing. A wider outage could also come from a local cause such as a power cut, a storm or a cyber attack. During the Iberian blackout of April 2025, for example, mobile networks struggled and card payments went down.

If the internet and mobile data stopped working where you live, you might lose:

News and alerts from apps, websites and social media
Messaging and calls over apps like WhatsApp
Card and phone payments, if shops’ terminals cannot connect
Online maps, banking and prescriptions
Smart home devices, alarms and some heating controls
Work, school and streaming that depend on the cloud

The aim is not to replace the internet. It is to keep the essentials working for a few days.

How to stay informed and in touch without internet

Sweden’s crisis information service, Krisinformation, gives some of the clearest advice on phone and internet outages:

Use radio. In Sweden, the P4 channel of Swedish Radio is the emergency channel. Keep a radio that runs on batteries, solar power or a hand crank.
Call 112 in an emergency. The call may connect through another operator’s network. If it does not, Krisinformation suggests removing the SIM card and trying again, or going to the nearest fire station.
Keep power for your phone. Have spare batteries, a charged power bank and a car charger.
Write down important numbers. Keep a paper list at home.
Spread the risk. A household with contracts on different mobile networks has a backup if one fails.

Ready.gov in the US also lists a battery or hand-crank radio, local maps, and a phone charger with a backup battery in its basic kit.

Need	Without internet	Do this now
News and warnings	Battery, solar or wind-up radio	Find your national emergency station and note it down
Directions	Paper map or offline phone map	Download offline maps of your area
Contacts	Paper list	Write down family, doctor, school and neighbours’ numbers
Payments	Cash	Keep small notes and coins at home
Meeting up	Agreed meeting place	Pick one near home and one further away
Documents	Paper copies	Print prescriptions, insurance and ID copies

Our family emergency communications plan post explains how to set up meeting points and a contact list. For lighting and phone power during a power cut, see our power outage preparation guide.

Checklist

A few days of supplies also helps if an outage comes with other disruption. Check how many days your household would last with our free calculator.

Cable breaks are routine and usually fixed quietly in the background. If services do go down, listen to your local radio and follow the advice of your local authorities.

Sources & further reading

Every fact in this post was checked against the sources listed above on 1 November 2026. Advice changes: always follow your local authorities.