That page hints at it, but they don't mention that Polynesians used one of the most sensitive wave detection instruments available: the navigator's own testicles.[1]

Besides mapping wave interference patterns as they refract around islands (note the similarities between the second stick chart and the diagrams in [2]), the Polynesians also used "the stars [also using stick charts], driftwood, clouds, seaweed, winds, birds, weather, the smell, taste and temperature of the ocean, ... and the olfactory sense of an on-board pig."[1]

The most curious method however is with "te lapa," a phosphorescent phenomenon that appears as 'underwater lightning' pointing toward islands. The phenomenon is not fully understood even to this day, but it could be related to constructive interference of seismic waves.

Their development of sophisticated navigation makes sense from a business perspective. The Polynesians maintained numerous trading routes between islands, so there was a lot of technological pressure to develop better navigation methods. If even 10% of your boats didn't come back it would be disastrous for the endeavor.

[1] http://www.ifa.hawaii.edu/friends/Technology_of_Oceania.pdf

[2] http://www.coastal.udel.edu/ngs/waves.html

[3] https://www.jstor.org/stable/pdf/23041479.pdf

I'd never seen Polynesian stick charts before, they're incredible. Thanks for sharing!

You may like this article then. "The Secrets of the Wave Pilots"

https://news.ycombinator.com/item?id=11320127

"...the Marshallese use stick charts, wood frames crosshatched like dream catchers to represent swells coming from four cardinal directions, with shells woven in to symbolize the position of the atolls."