Well, it seems to me that sailing indicates some kind of directed propulsion whereas floating is just launching yourself for whatever reason and going wherever the waves and wind take you.
OK...I'll buy that.
I do have a problem with a hominid just launching off into the sea on a log..or log raft. Neanderthals weren't essentially stupid or reckless.
My thoughts go here. The Neanderthal in all probability had no sail....nor did they have any ability for navigation.....they certainly couldn't swim that far.
Island to island seems plausible....however...
and please excuse me....I'm just trying to catch up a bit.
I think it was a long walk.
The first Neanderthal was a "Homeless Drifter".