I had previously thought the colonization of the Americas from Asia to be economically unfeasible given the great logistical hurdle it presented. I changed my mind recently after coming across the Kelp Highway Theory of Native American migration.
The idea is some of the ancestors of Native Americans didn't cross the Bering Strait, rather they went by sea and fed themselves off a stretch of kelp forrest that is nearly continous from Japan to Alaska, and down the California cost to Mexico. The kelp itself is edible but it also contained an ecosystem of fish, clams, sea otters, and bird species which was able to sustain a transpacific human migration.