But the route from Polynesia to Madagascar can be traveled along the shoreline of Asia and Africa, so can be completed without navigational aides. The crossing from Africa to South America is 3000 km of nothing but ocean.
Amyr Klink crossed the Atlantic in a rowing boat from Namibia to the north coast of Brazil in 1984, it took him around 100 days [1]. He seems to remain the only one to have accomplished such a feat. Very little information in english seems to be avaiable though. The boat can be seems in the background of this video [2] (in portuguese).
According to their oral history, they went clear across the ocean. My source is "A History of Madagascar" by Mervyn Brown (2001) and it could be incorrect, I didn't seek out the primary sources.
There is documentation that the pacific islanders crossed thousands of miles of ocean successfully on a fairly routine basis.