Ah, but were their language capabilities sufficient for the mastery of nautical jargon?
According to New Scientist:
Strasser agrees Neanderthals were seafaring long before modern humans, in the Mediterranean at least. He thinks early hominins made much more use of the sea than anyone suspects, and may have used the seas as a highway, rather than seeing them as a barrier. But the details remain lost in history. Any craft were presumably made from wood, so rotted away long ago.