At https://phys.org/news/2019-11-newly-motifs-art-tumlehed-seafaring.html … newly discovered motifs in rock art in Sweden show stone age seafaring was a fact. We know that Mesolithic people used boats as a boatyard dating back 8000 years ago was found in the Solent (under the sea and close to a cliff face). However, these mobile hunters in Sweden appear to be related to people akin to the Finns as similar motifs are known from Finland and the Koala Peninsular in Russia – as well as the northern regions of Scandinavia.
… spectroscopic dating of the images has come up with a date somewhere between 6000 and 4500 years ago – contemporary with the megalithic period in north west Europe. What this seems to show is that using boats to hunt marine animals was not just a feature of the Mesolithic in Atlantic waters but was common also to Arctic waters – and the big question might be, how much further into the past were boats in use in Europe and Siberia. If it was common practise in the Late Glacial Maximum (when Siberia was apparently warmer than today) it would influence the migration theories of people entering the Americas. In this instance, the researchers were looking at the megalithic period in general (and cave art was considered a possible clue on the people involved). The cave concerned is on an island near Gothenberg – where there are lots of prehistoric rock paintings. Many motifs were found – and pictographs of boats with elk head stems were fairly common.