> Polynesian languages would distinguish between fresh water bodies and salt water ones

Māori distinguished water _quality_ without reference to whether or not it was a lake or sea or river.

Wai tai: Salt water

Wai māori: Fresh water, water for regular daily usage

Waiora: Pure water that restored/healed a person

Waikino: Dangerous / polluted water

Waitapu: Sacred water

Which makes sense right? You can have a river that is significantly salty and hence unpotable some distance from the sea, depending on the strength of the tides - likewise you can have a lake near the sea that intermingles with seawater to the extent that it's brackish.

So Māori naming was more based on utility than the geographical distinctions than we're used to in the Eurocentric worldview.

And this also extended to their view on land ownership, which caused so many issues when Europeans turned up and wanted to "buy" "land" from the local iwi/tribes - a chief would grant a European the exclusive rights to grazing in an area, and the European would interpret it as exclusive ownership, and then get angry when the Māori would continue harvesting tuna/eels or birds on "their" land that they'd "purchased".