A Delta police officer has undertaken a marathon of a swim, all to help a cancer patient.

Kelly Seib of the Delta Police Department is aiming to swim for 12 hours straight – eating and drinking while treading water – to raise money for a brain cancer patient Tashina Janus, who needs treatment that's only available in the U.S.

Seib started at 7 a.m. on Thursday, only taking two minute breaks to change out of her wetsuit and go to the bathroom.

"I only had three months to train for it, which isn't a significant amount of time for it," she said from the pool.

Janus, who is the sister of a fellow Delta cop, is hoping to go to the U.S. for treatment that isn't available in Canada and can run well into six figures.

"It takes a load off my shoulders as well as my family's shoulders," says Janus, when asked about Seib's fundraising efforts. "We don't have to worry about the financial aspect. We just have to worry about my life and living day-by-day and getting better."

Seib says she was partly inspired by her uncle, who died of brain cancer and suffered similar symptoms to Janus.

"There are some (cancers) where doctors can't do anything – like my uncle - but with hers, there's hope," she said.

Despite what may come next, Janus says the pair have formed a strong bond.

"We did not know each other a few months ago but now we're bonded and she is my sister," she said.

With files from CTV Vancouver's Breanna Karstens-Smith