As far as I am aware, the current conventional thinking on the subject is that the populating by humans of Polynesia, Hawaii and South America happened much, much more recently than any possible land bridge could have existed (except the Bering land bridge from Asia to Alaska). (Australia is a different story.) So I don't know how Polynesia could have been reached by its first inhabitants except by seacraft. I am not saying this to be disagreeable - I am just curious what you are suggesting.
When Columbus hit the Caribbean Islands he encountered large long sea-going inter-island canoes. None of these were ever seen on the open ocean nor reported to have reached Europe, 2800 miles away. What prevented these Caribs from reaching Europe before Columbus?
Are there records of any other peoples duplicating the supposed ocean journeys of the Polynesians?
No evidence? Ergo, no theory is plausible, merely conjecture.
Even the Egyptians and the Chinese were coast huggers.
The proof is in the pudding ocean