This question was answered on our Q & A Wednesday show on July 19, 2017.
It is customary to pay gratuities to onboard crew. While the amount of the gratuity used to be solely at the discretion of the guest, today all cruise lines have a standard daily amount that they will charge to your onboard account automatically. The gratuity that you pay will go to the crew that you come in contact with on a regular basis, such as your room attendant, waiter and assistant waiter. Aside from the fact that crew members rely on gratuities for a large percentage of their pay, you should feel free to adjust this amount higher or lower, based on the actual service you receive. More likely than not, you will find that the level of service exceeds your own expectations and your gratuities will be well deserved by the individual crew members.