To your question, crew have set rules about interacting with passengers and can loose their jobs if seen in cabins regardless of whose.
Meeting on shore is not an issue normally but one still has to be discreet.
A lot of ships excursions will have a crew member or two onboard the tour bus who represent the ship and they help the driver or guide and depending on their role can be responsible for your presence or not.
Remember that they work on that ship for a few months at a time and you are only present for a week or so. If you wish a relationship be discreet and respect the rules as if they loose a job because of you , they have to pay their way back and their family is out expected wages.
Just because they are friendly to you on the ship do not expect that to be so on land when they are off duty as they might think you are placing them in an awkward position. DO not force anything , be patient and respectful
Sure, you might meet the love of your life, time will tell
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