My husband drinks unsweetened almond milk which is hard to find (usually only the sweetened version is available). For our 2 week Panama Canal cruise last year we wrapped a bundle of boxes in heavy duty Saran Wrap (LOTS), and put them in a cardboard box to check as luggage on the plane. We carried them on the ship. This worked like a dream, despite one box leaking very slightly. Because we had so many layers of plastic wrap it was contained and the box stayed dry. On a short cruise you probably don't need as much as we did, but I wanted to share that it's totally doable!