She previously served in the Senate from 2011 to 2017, resigning during the parliamentary eligibility crisis due to her holding Canadian citizenship in violation of Section 44 of the Constitution of Australia.

[4] Waters was the Greens' Brisbane Central Candidate in the 2006 Queensland state election running against then Premier Peter Beattie, securing almost 5,000 votes.

[9] Waters was forced to resign from the Senate on 18 July 2017, after it was uncovered that she was a dual Canadian-Australian citizen, thereby making her ineligible to be elected under section 44 of the Australian Constitution.

[13] On 8 August 2017, Waters announced that she had renounced her Canadian citizenship and declared her intent to stand for Greens preselection and return to parliament at the next federal election.

[15] On 3 April 2018, Waters was announced as the Queensland Greens lead Senate candidate for the next federal election, with Andrew Bartlett instead opting to contest the lower house seat of Brisbane.

[16] On 16 June 2018, Bartlett announced that he would resign from the senate at the end of August, and Waters was preselected to fill the resulting casual vacancy ahead of the election.

In March 2021, Waters issued an apology to Federal Minister Peter Dutton for comments made on Twitter accusing him of being an "inhuman, sexist rape apologist".

[25] Waters has another child born in 2016, who made Australian political history becoming the first baby to be breastfed in the Senate chamber in 2017.