Boat passenger traffic ticked up 4% last year, to 538,000. Although largely for domestic cruises, 10,000 passengers traveled on international Black Sea routes, largely to Odesa. This summer, Viking River Cruises expand its 10 Odesa-Kyiv cruises to include Bucharest. The 12-day cruises run from May 17 to Aug. 15 and prices start at $4,000 per person.