Why is Nami considered a Vastaya?

The vastaya tribes have many different forms stretching across terrestrial, arboreal, aquatic and aerial creatures.

How else would you actually have a human/fish hybrid? Despite all the myths about them, they don't have much reasoning to their existence beyond the typical "a god did it" or the impossible "a human mated with a fish or something???". As a magically transformative being you can have anthropomorphic animals and impossible hybrids without avoiding explaining it or using the traditional cop outs.

Is she now a woman in a fishes body? Like Klaus?

Darnit CIA Stop putting people in fishes bodies.

Vastaya are chimeric animal people. Fish are animals.....

I've always assumed she was a mermaid

Vastaya = animal ppl Fish version of the vastaya = the Marai The marai = nami's tribe Therefore, nami = vastaya

In very, broken down, possibly over-simiplified layman's terms.