You won't need cash on board the ship- your Seapass is all you will need- it is your ID, your door key and your charge card for onboard spending... the only place you will need cash is in resorts.
You can pay your account at the end of the cruise with cash or credit card.
If you intend to pay in cash they will ask you to deposit a certain amount at the start of the cruise.
The best way at the moment is $ cash as the $ is weak & credit cards charge you interest & on travellers cheque you have to pay a fee debit cards are not normally accepted as there is no electronic connection to your ban.
Debit cards are not accepted (in theory) - cash or credit cards only on board RC.
We are travelling on the Independence of the Seas in May and don't have any credit cards. We use debit cards. How will that affect us when paying for our bill.