If you book in advance you pay when you pay your cruise fare or when you book the excursion. If you book on the ship at the excursion desk or remote TV the fee will be on your ship board account. Enjoy looking at all the excursions.
Shore excursions booked on the website when you log in and see your reservations and available excursions are paid by on your credit card at the time of booking. If you book your excusion now and are not going until October then you will see it on your credit card statement, but it also appears as a debit and a credit on the sail and sign if you did book it and pay in advance.
2007 Victory & Triumph
2008 Conquest & Liberty
2009 Valor, Freedom, and Splendor
2010 Glory and Liberty