A travel eSIM works on a cruise in port and near land, where your phone can reach the local mobile networks. Out at sea there are no land towers, so the internet comes from the ship: its Wi-Fi runs over satellite, and more and more lines, including Royal Caribbean and Japan's Asuka II, now use low-orbit Starlink for it. Any mobile signal your phone picks up at sea belongs to a separate maritime cellular network carried on the ship, which only switches on once the vessel is outside territorial waters and is billed by your home carrier as roaming, outside your normal plan. This guide uses cruise lines' own pages, mobile carriers and EU rules to explain how ship Wi-Fi and ship cellular work, and how to split your time between ship Wi-Fi and an eSIM in port.
To be online as soon as you step off in port, install an eSIM for the countries on your itinerary before you leave home. Browse the Coral eSIM plans and pick the country or regional plan that covers your ports.
Cruise ship Wi-Fi runs over satellite, and many lines now use Starlink
With no base stations in the open ocean, a cruise ship's Wi-Fi reaches the internet over satellite links. Services using satellites in low Earth orbit have spread quickly in the last few years.
- Royal Caribbean: its official guide says every ship offers its VOOM Wi-Fi via SpaceX's Starlink, and that because it runs over satellite it works whether you are far from shore or about to dock.
- Princess Cruises: in an August 2024 announcement, Princess said its MedallionNet Wi-Fi combines several satellite constellations, including Starlink, with 5G on land. The top tier, MedallionNet Max, gets prioritized access to the best-performing bandwidth, which is typically Starlink.
- Asuka II: since 13 February 2024 all guests have had Wi-Fi over Starlink provided by KDDI. The official page says the Wi-Fi is free and covers all cabins and public areas except the Deck 12 Grand Spa and the fitness centre.
- Asuka III: uses Starlink for its free onboard Wi-Fi and sets no daily data cap.
Whether Wi-Fi is paid or free, and how many devices you can connect, depends on the line, the cabin and the package, so check your own cruise line's page before you sail.
What cruise ship Wi-Fi cannot do: limits the lines state themselves
Starlink has made ship Wi-Fi much faster, but it is still not the same as fibre on land. The official Wi-Fi pages for Asuka II and Asuka III list the following:
- Because it is satellite, speeds may be restricted depending on how busy the ship's connection is
- It is not suitable for anything that needs real-time reliability, such as securities trading, government procedures or online meetings
- Apps and websites with regional restrictions may not work
- It may be unavailable outside satellite coverage, because of communication regulations in individual countries, during bad weather or terrain interference, or during maintenance
- Laptops can have trouble connecting because of security software, so smartphones and tablets are recommended
On Asuka II a single session lasts up to six hours, and the number of devices per cabin is capped at three to five depending on the cabin type. Royal Caribbean also notes that weather and some polar regions can temporarily weaken the signal. If you need a reliable connection for work, plan to use a land network on port days.
Why your phone works on a cruise at sea: the maritime cellular network
Many cruise ships carry a small mobile base station on board, linked to land by satellite. The best known is Cellular at Sea, which says it operates on more than 210 cruise ships. According to its official site, service starts once the ship reaches international waters, and your phone shows "Cellular at Sea" or "901" as the network name. Your home carrier bills you under your plan's international roaming terms, the same as it would in a foreign country.
Royal Caribbean likewise says phones connect at sea through "cellular at sea" and that roaming rates are set by your own provider. SoftBank's list of partners for its onboard service names two operators: WMS in the United States and Telenor Maritime in Norway. In other words, the signal at sea does not belong to any country's land network; it is a separate network built for ships.
Ship cellular only switches on outside territorial waters
Maritime networks are restricted so that they do not interfere with land networks.
- SoftBank: from the port to the edge of territorial waters you use the coastal country's networks; its onboard service starts once the ship crosses into the high seas.
- Princess Cruises: Cellular at Sea is available once you are in international waters.
- EU rules: Commission Decision 2010/166/EU on mobile communication services on board vessels (MCV) says the system must not be used closer than 2 nautical miles from the baseline, and that only indoor antennas may be used between 2 and 12 nautical miles. A 2017 amendment added UMTS (3G) and LTE (4G).
Cellular at Sea's site adds that service can drop temporarily as the ship enters or leaves port or moves closer to land, and that this is normal. Near the coast your phone latches onto the coastal country's land networks; further out it switches to the ship's network. That is why phones connect to unexpected networks during a cruise.
Japanese phones on a cruise: even a round-Japan cruise can reach the high seas
SoftBank's onboard service needs no sign-up: any line that can roam abroad connects to the ship's network on the high seas. Pay-as-you-go data was discontinued in October 2023, so data now works only through its "Kaigai Anshin Teigaku" roaming package. SoftBank also states that even passengers on a cruise around Japan may sail through the high seas and end up on this service. A domestic trip on land can still mean an international-style network at sea.
NTT Docomo ended its own maritime roaming service in January 2022. It still warns, however, that if your carrier selection is set to "automatic" in coastal areas or on a ship, WORLD WING international roaming or maritime roaming charges may apply and bills can be high. Customers who want only the domestic network are told to set the carrier to Docomo manually in the phone's settings.
Whatever your carrier, assume that the signal at sea sits outside your normal domestic plan. For how roaming charges are structured, see international roaming vs. eSIM.
How to set up ship Wi-Fi and your eSIM on a cruise
Once you decide on ship Wi-Fi at sea and a travel eSIM in port, set up your phone in this order.
- Install the travel eSIM at home before you leave: trying to set it up for the first time in port, with no connection, is slow and awkward. See how to set up a travel eSIM.
- After sailing, turn on Airplane Mode and then switch Wi-Fi back on: Cellular at Sea says its service needs Airplane Mode off and international data on. Do the opposite and your phone will not use it.
- Turn Data Roaming off: on iPhone, go to Settings, then Cellular, then Cellular Data Options, and turn off Data Roaming (Apple's guidance). On Pixel phones, go to Settings, then Network & internet, then SIMs, and switch Roaming (Google's guidance). Menu names vary by manufacturer.
- In port, turn off Airplane Mode and set your travel eSIM as the data line: on iPhone, choose the line under Settings, Cellular, Cellular Data. Keep Data Roaming on for the travel eSIM line.
- Check the network name: if it shows a carrier from the country you are visiting, you are on land. If it shows "Cellular at Sea" or "901", you are on the ship's network, so go back to Airplane Mode.
- Turn Airplane Mode back on before the ship leaves port: as you sail away, your phone will move from coastal networks to the ship's network.
If your cruise calls at several countries, a regional plan that covers all of them is easier than buying an eSIM for each port. For choosing a plan by itinerary, see using an eSIM on a cruise. You can find plans for your destinations on the Coral eSIM plans page.
Cruise Wi-Fi and eSIM: frequently asked questions
Does cruise ship Wi-Fi work while the ship is in port?
It depends on the ship. Royal Caribbean says its satellite Wi-Fi works even when you are about to dock. Asuka II and Asuka III, on the other hand, note that it may be unavailable because of individual countries' communication regulations. In port, a travel eSIM on the local land network is the more dependable option.
Can I join video meetings or stream on ship Wi-Fi?
Ships using Starlink are much better than before, but the official pages for Asuka II and Asuka III say the Wi-Fi is not suited to real-time uses such as online meetings, and region-restricted streaming services may not play. Plan important calls for port days on a land network.
What does "Cellular at Sea" or "901" on my phone mean?
It is the maritime cellular network carried on the ship. It works in international waters, and your home carrier bills you for it as roaming. If you do not want to use it, turn on Airplane Mode or turn off Data Roaming.
Can my phone connect to the ship's network on a cruise that stays in Japan?
Yes, it can. SoftBank says passengers on a cruise around Japan may use its onboard service when the ship sails on the high seas, and Docomo warns that international roaming charges may apply on ships and along the coast. Even on a domestic cruise, Airplane Mode plus Wi-Fi is the safe setting at sea.
Does a travel eSIM work while the ship is at sea?
Plan to use your travel eSIM on the land networks of the countries where you dock. At sea, use Airplane Mode with ship Wi-Fi, and start using the eSIM only once your phone shows a carrier from the port country.
Use ship Wi-Fi at sea and your eSIM in port, and a cruise stays simple
Satellite links such as Starlink have made cruise ship Wi-Fi far more usable, but it is still a connection shared by the whole ship, and the lines themselves say it is not suited to online meetings. The mobile signal at sea comes from a maritime network that only runs outside territorial waters and is billed as roaming outside your usual plan, even on a cruise around Japan. Keep your phone in Airplane Mode with Wi-Fi on while sailing, and switch to the travel eSIM you installed at home when you reach port. Decide on that split before you board and connectivity will not catch you out.
Find a plan for your ports of call on the Coral eSIM plans page.
