I read an article that suggested Vortigern changed his name from Vitalinus to bring back the pre-Roman rule of the 'Cymri' the Cambrians, that are mentioned in the Bible, and appear to be kin the the Skythians who lived on the Black Sea. Surely they were about this sea in boats. I also read of a waterway from the Black Sea to the Baltic Sea, it commonly traversed via rivers that were connected by lakes that have since disapeared.