No. You will not be charged if the cruise ship is late or is unable to make a stop in Grand Cayman. You will also not be charged if the excursion operator had to cancel the trip due to bad weather or equipment failure. There is always the chance that the ship will not make it to Cayman if the weather is not good. This is usually the exception rather than the rule and although not guaranteed, the chances are that you will dock here. Although your credit card number is asked for at the time of making a reservation, it will NOT be billed if your cruise ship does not dock as it wouldn't be fair.