If you have to communicate, and your phone is equipped with wifi...buy the internet minutes, turn your phone to Airplane mode, and use email. This option is much easier than toting a laptop without paying additional charges.
I found this an easy way to keep in touch, via email.
If there is a real emergency back home, they can call the ship themselves.
You won't be charged roaming while in Airplane mode. Worked for me on my Sprint Palm Pre.
Someone please correct me if I am wrong as I do not know the ways of different carriers.