[SauronOfMordor]

They would have had to tow extra boats from their home port “shipyards” and then would have had to portage/carry them to the lakes so it is impossible”.

The distinguished gentleman should read the chronicles of the Lewis and Clark expedition. They managed.

If the trade was a regular thing, then the boats/canoes/whatever, once built or otherwise gotten there, would have been making the back and forth trip regularly.

[Openurmind]

Absolutely and so did the natives long before...

That was one of the silliest things I have ever heard yet.