The reason I asked about boats is that my preferred passage would be very different depending on the kind of boat. Small versus large, power versus sail. I'd also like to know from where in Siberia you were thinking of leaving. According to Encyclopedia Britannica
, Siberia borders both the Pacific and Arctic oceans. So, if you're in the Northwest portion of Siberia, you'd probably take a very different route than if you were in Eastern Siberia.
Looking at a map of the ocean currents like this one:
You can see that the current on the eastern cost of Siberia (i.e., the northwestern Pacific) tends to flow to the south. However, by the time you get to Japan, the current turns against you and starts to flow to the north. Motoring/sailing into that would be like walking into a headwind, and you're going to lose speed. It may not be much in an absolute sense, maybe a few knots/miles per hour. For some vessels, that may be fine, but for a sailboat, where the maximum speed is typically less than 10 knots (most say to assume a 5 knot average speed for long passages on a sailboat), a 2-3 knot drop is easily a 20-30% speed reduction. What seems to me to make more sense would be to ride the Kurishio current southeast, away from Japan for a while (probably somewhere around the Midway Islands, though you may not need to go QUITE that far). Then head southwest with the intention of picking up the equitorial currents.
Now, the above assumes good weather and a stout boat with lots of fuel and water carrying ability.
As for a slower route, well, if you were to leave from northwest Siberia, you could, as mentioned above, try to take the route around the arctic, but depending on the time of year, you might get ice bound. Once you're free from the ice, heading down the coast of Europe to the Equitorial currents, and then hitch a ride across the Atlantic to Panama. Go through the Panama canal, then ride the Equitorial current across the Pacific to Australia.
You could also go down the cost of Europe, then cross the Equator and head south along Africa. You'd fight the current all along the African coast, but then you could pick up the Antarctic circumpolar current and ride that over toward Australia.
Does that work for a somewhat more serious answer?