You can never have too much cash traveling outside of your home country and away from your home bank. Each year our credit cards get more reliable and predictable away from home. There is never a weeks long guarantee there. We always carry enough cash to no use our credit cards. A network, security, scam, or political diplomatic tiff can render the cards in your purse or wallets worthless in seconds. You simply cannot count on them. The AMEX Card was originally built around cash and mail away from home. The benefit remains to members today. The hitch, you must travel to the AMEX office or other possible location of AMEX's choice and sit across a desk to cash one of your personal checks. AMEX does charge fees for that member privilege. My two cents. Never take the credit cards as a given guarantee. Do not use your credit cards anywhere near the ferries.