well we actually would have wine dark seas then.

(https://en.wikipedia.org/wiki/Wine-dark_sea)

The sentence explaining "purple" does not make sense:

> For instance, should levels of sulfur increase, the oceans may appear purple due to intense volcanic activity and low oxygen in the atmosphere.

Increased levels of sulfur causing volcanic activity? Michael Crichton's words come to mind:

> I call these the "wet streets cause rain" stories. Paper's full of them.