How did the design of the viking long boats allow them to have easy access inland?

Well, viking ships were meant to be slender and flexible making easy access to inland entrance.

In this article it states, "One particular advantage of the Viking ship is the comparatively low weight, making land transport and portage routine, as in crossing Jutland instead of rounding Skagen to enter or exit the Baltic Sea, and travel on the river networks of Eastern Europe."

Hope I could help!

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