Comment by EdwardDiego

Yep, it's the same in Māori, a Polynesian language, where "moana" refers to oceans and large lakes alike.

What's really interesting is that in Hawaiian, a close relative with some sound shifts (k/t, l/r, n/ng, so taboo is kapu in Hawaiian, in Māori, tapu, path is ala / ara, the God of the sea is Kanaloa/Tangaroa) they have more than one word for ocean, kai is coastal waters, moana is the deep ocean.

But it makes sense in the geographical context of both societies and how they evolved to their environment, the Hawaiian archipelago is made up of multiple smaller islands separated by waters exposed to the full force of the Pacific, while the archipelago of New Zealand is dominated by two large landmasses separated by a narrow strait that together are about the same area as Germany.

So the Hawaiians remained more tightly wedded to the sea to build their archipelagan societies than the Māori did.

In fact, the Māori lost the knowledge to build ocean-going vessels like the ones that had carried them to New Zealand within a few hundred years because there was no need for it. And their language lost the distinction between "coastal waters" and "ocean" while Hawaiian retained them.

While we have evidence of Māori traveling to Raoul in the Kermadecs early on, as classical Māori culture evolved on much much larger islands, their technology focus on boats switched from ocean going vessels to coastal travel and river travel.

In fact, while "Wai", water, is often considered the Māori word for "river", there's another word that also means river in Māori:

"Ara" - path.

(Of course, it still means a regular path)