Since I am a French citizen I can apply for the eVisitor (subclass 651) visa. However, there is something that seems a bit ambiguous. On the Australian government website it is written that with this visa you can stay: "for up to three months at a time within a 12-month period."
Does that mean that someone with this visa could spend 3 months in Australia, fly to another country, and then come back the day after to stay 3 more months? It seems more likely to me that in reality it means you can stay up to 3 months in total in Australia over a period of 12 months, but I still wish for another opinion on the matter.
I'd like to plan a year long trip to Australia. I'm currently looking at the different options to do that.
EDIT: I was able to confirm Newton's answer. It is possible to travel back and forth from Australia every 3 months with an eVisitor visa. However, Peter Green's comment was on point as well. The border guards were very inquisitive about my repeated visits. They searched my phone and my laptop. That was not a pleasant experience.