10. Not bringing cash. 

Unless you’re not planning to leave the ship or you're signing up only for the ship's tours, you’ll need some money in port — especially for those small towns in Europe and parts of Asia where many establishments don’t take credit cards. Instead of spending your very limited time onshore scrambling to find an ATM or a change bureau, it’s handy to have some local currency on hand, which you can get on your pre-cruise night or from your bank at home. Although some cruise ships may have some for exchange, it’s wise not to count on it.