system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did ancient peoples make it to Hawaii and other geographically disparate islands centuries before reasonably modernized shipbuilding?

I'm not talking about riding a ship over a few dozen miles. I'm asking how people navigated thousands of miles of treacherous open ocean before sails were even commonly implemented. Ships in the 1400's and 1500's were still dodgy risks.
gpt
On a boat. 

The Polynesian people lived on strings of islands for thousands of years, some islands that were close together and some that were further away past the horizon. They were experts at seafaring, had excellent boats, excellent navigation, and understood the cyclical way the ocean current and winds changed over the year to let them go far out and then circle back. They knew what supplies to bring, how to get fish and fresh water on long trips. They could spend weeks at sea.