They're offered as 'cruises' these days; you'd be looking at rates of ~$100-150/day, and they do single-day port calls wherever the ships' routes make a call. I

They're offered as 'cruises' these days; you'd be looking at rates of ~$100-150/day, and they do single-day port calls wherever the ships' routes make a call. It looks like you do have to book fairly far in advance, though.