The ship-like things drawn on the rock arts aren't ships but Stone humans !
The rock art of ship-like thing
This is the rock art which is regarded having drawn the ship several men on board.
（ Fugoppe cave and Rock Carvings in Tanum in Sweden ）and so on show the giant Stone gods extended long and alter egos who had splited up from Stone gods were connected on it.
Fugoppe cave
http://3step.me/36b0
Rock Carvings in Tanum in Sweden
http://norrsken.jp/guide/sweden-world-heritage/tanum/
Many rock arts
http://3step.me/36b1
http://slicer93.mbsrv.net/fune1.jpg
http://slicer93.mbsrv.net/fune2.jpg
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Fugoppe cave
http://slicer93.mbsrv.net/fune4.jpg
http://slicer93.mbsrv.net/fune6.jpg