If your cruise data package is MB-based (as opposed to minute-based), be sure that you have all automatic updates, uploads, downloads, and similar turned off. Especially if you're gone for a few days, here's what can happen: You turn on your Windows laptop the day after Microsoft "patch Tuesday" and it downloads 100mb of Windows updates in the background. Meanwhile, you connect your iPhone and it uploads all of your pictures you've taken over the past few days up to the cloud. These things can exhaust even a large Internet package in a short period of time. If you have everything that uses data in the background turned off, you can get a surprising amount of normal stuff done without using a lot of data.