We have historical evidence of remarkable voyages in these waters in boats little different from what might have been available to ancient peoples. Lieutenant William Bligh in the launch of HMS Bounty made a voyage of 3,600 nautical miles to Timor with other crewmen of the Bounty. Survivors of HMS Pandora (with some Bounty muniteers as prisoners) made a much shorter voyage from the Great Barrier Reef to Timor.
Polynesian voyages were made throughout the Pacific on boats made of local materials. We will likely discover that such voyages were made by ancient peoples thousands of years ago from Asia to North America and from Europe to North America. The absence of physical evidence have led us to underestimate the sea faring capabilities of these people.
Yeah, the isolationists are a bunch of landlubbers. Even Britain, which was connected to the European mainland until 200,000 years ago, has to have been colonized by sea, repeatedly, and in historical times it has been colonized and/or conquered multiple times (Claudius' cross-channel invasion was the largest until D-Day). One of the scholars of ancient language (I'm drawing a blank, and forget about my finding the book just now) recounted a joke about how the first Britons didn't come in from outside, but were symbolically transformed reindeer.
Since the ocean level was lower during glaciations, any trace of early occupation of Pacific Islands would have been submerged long ago. That's not a permanent condition, but many if not most of the isolated islands are uninhabited, or only sparsely inhabited, and going to one of them for scientific purposes would be expensive and non-trivial.