We've met several single travelers on our prior cruises in addition to making new friends on virtually every cruise we've done with Viking.  Excursions is one way to meet and get to know others.  Pre-dinner cocktails is another.  And we've had a wonderful time at The Restaurant when offered a shared table - when you get to the restaurant, let the maitre'd know you'd be willing to share - they will ask folks coming in if they'd be willing to share with you.  Done that a few times and have had won