Humans settle along coasts, which after the ice melt are submerged and which is why trawlers regularly find ancient animal remains and human artifacts from the now submerged area known as "Doggerland" in the North Sea:
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.
We have learned how to do archaeology in the Black Sea and we can use these techniques to do the same thing along the Pacific coast of the Americas, Pacific islands, and Australia. It will require better remote sensing technology, since finding ship wrecks via remote camera will not work for the next stage of exploration, but that will come.