You can certainly use your iPhone on a cruise ship, but you must be extremely careful to avoid massive roaming charges. Once the ship is about 12 miles out at sea, it connects to a maritime satellite network (often appearing as "Cellular at Sea" or "901"). These networks are not covered by standard domestic plans and can cost upwards of $6 per minute for calls and over $10 per MB for data. The safest way to use your iPhone is to keep it in Airplane Mode and then manually turn on Wi-Fi. Most cruise lines in 2026 offer Wi-Fi packages (ranging from $15 to $30 per day) that allow you to use iMessage, social media, and even Wi-Fi calling. Some modern ships equipped with Starlink offer speeds fast enough for FaceTime and streaming. If you plan to use your phone in port, consider an eSIM for local data, but always re-enable Airplane Mode before the ship sails to ensure your iPhone doesn't "hunt" for a satellite signal in the background, which can lead to a "bill shock" of hundreds of dollars upon your return.