"Viking longboats were shallow draft vessels that could be sailed or rowed up narrow waterways & beached."
A couple of those rivers would be the "Seine" and the "Volga."
The words "Rus" and "Slav" are nordic in origin, given by the Swedish Vikings that invaded and dominated Russia, for a long time.
Viking traders were operating in the Black Sea. The Byzantine Emperors' "Varyngian" bodyguards were probably Norsemen. Also, the Norse conquered and ruled Sicily for a time. They were operating a LONG way from home waters.
Yeah, they claim the Vikings went all the way down to the Caspian, via river passage and portage, trading furs (for kittens?).