Straight Talk does not operate with any international carriers, including cruise ships.
Excerpt from Terms and Conditions:
International Roaming is strictly prohibited. Straight Talk does not offer international roaming or international long distance service. You will not be able to make or receive calls on your Straight Talk phone if you are traveling outside of the United States. Any attempt to place or receive a call on your Straight Talk phone while traveling outside of the United States could result is service deactivation and account termination without a refund for unused service.