well, as I will be on my frist cruise in July with my teenage son, I won't have a man around who can keep the credit cards, etc. in his wallet.
So I will be bringing my cheap black wal-mart bought shoulderbag which is about 8 inches long, 5 inches high and 4-5 inches deep. It has a long, thin attached strap that lets the purse hang down to my abdomen so I can basically wear it over/across my shoulders the whole trip. I will have my cash, credit cards, cell phone, pda, digital camera with great video capacbility, brush, minimal makeup, prescriptions, sunglasses, and important docs with me (i.e. copy of passport, excursion confirmations).
I don't plan to go swimming or do any water sport excursions. With this type of purse, my hands are free. My son can wear the binoculars around his neck on excursions.
I will be bringing a large tote so when I'm hanging around the ship during the day following my son around as we engage in activities, I can have my purse inside it as well as a spiral notebook (I'm a writer) and sunblock.