And science:

The Hawaiian archipelago is a chain of giant shield volcanoes that arose via the activity of a "hot-spot" below the ocean floor. This "hot-spot" has probably been actively erupting lava for perhaps as many as 70 million years, if the Emperor Seamounts are considered part of this chain. The Hawaiian Archipelago has formed as the ocean floor has moved across this "hot-spot" in a northwesterly direction. There are at present 132 islands, reefs, and shoals with eight main islands. This is the largest assemblage of volcanic islands that are the most isolated from a continental landmass than any other similar set of islands in the entire world. An island arises if the flow of lava is sufficient over time to build it up above the surface of the sea. As the sea floor continues to move, the island is carried beyond the lava fountains from which it was formed. Wind and water wear away the landscape and the island presses down upon its supporting floor and subsides. The aging islands possess the rugged and spectacular scenic grandeur that looks so magnificient on picture postcards.

Sohmer and Gustafson, Plants and Flowers of Hawai'i

In this book I also read that seeds could only come to the islands via "wind, water, or wing"--blown thousands of miles by a storm, carried by a bird taken off course, or washed ashore after floating for many weeks in sea water. If you look on a map it seems highly unlikely that this would ever happen at all, and in the course of the island's 70 million years, it is believed that it only happened some 300 times--that all the vegetation that the Polynesians found here was the result of those 300 chance encounters, spread out over 27-70 million years.