I treat my credit cards like tools -- I have six cards and they each have a specific job to do. I use one card for travelling overseas. I use a second card for recurring charges (eg monthly utilities). I use a third card only for online retail transactions (eg Amazon). A forth is for business use only.... etc Frankly I am not really concerned about fraud. It is easy to watch the charges and I am not liable for charges I did not authorize. If a card is compromised, it only inconveniences a small portion of my financial life. Subsequently it doesn't really concern me to use a card at the Ferry or any other establishment in the islands. I never, ever, use a debit card.

Also, the advice on phishing emails is dead on. If you are not familiar with this fraud approach, please read more online.