At some departure ports you may be required to complete a short health questionnaire prior to boarding. There are typically 3 questions on the form, have you had a stomach illness or cold in the last 24 hours etc. 

The first day of your cruise is a great time to explore the ship. A lot of guests head straight to the buffet for a quick bite to eat so it can get quite busy, consider checking out the deck plan or onboard newsletter to see what other dining options are available.