Lolita was kept in cramped environs, and her former tankmate Hugo died after smashing his head into the tank walls in what is believed to be a suicide, Ms Daals said.
"It's ludicrous to have such a huge, beautiful creature that travels hundreds of miles a day stuck in basically a bathtub."
Despite protests and court battles, Lolita remained at the Seaquarium with no release in sight, Ms Daals, 29, said.
In January, hundreds marched to the oceanarium to call for the orca's release.
In July, groups seeking Lolita's release reportedly sued the Seaquarium and its parent company Palace Entertainment, claiming the orca's living conditions breached the US Endangered Species Act.
"A demonstration like [this] has never been done before so I'm hoping that we gain as much global attention as possible and therefore put more pressure on Palace Entertainment," Ms Daals said.
Some protesters calling for Lolita's release had previously made placards asking 'could you live in a bathtub?' or drawing the orca in a bathtub, as an analogy for Lolita's tank, she said.
"So, I thought I'd put myself in one."
Ms Daals was planning to stage her demonstration in January. She was considering doing tricks whenever she wanted food, to "simulate" the orca's situation. Ms Daals would only leave the tub to go to the toilet.
Animal rights groups, including People for the Ethical Treatment of Animals (PETA), were helping her organise the protest, she said.