American rower Sonya Baumstein began an epic, 6,000 mile journey across the Pacific on Sunday (7 June). The 30-year-old set sail from Choshi, Japan and aims to arrive in San Francisco in four to six months.

With her parents and her boyfriend sending her off at the Choshi Marina, where her boat was docked during her preparations, Baumstein appeared mentally ready for the big trip.

"Is numb an okay answer? Because that's what I feel. I don't know. I never had anybody ask me right before I left before. I'm going through the five stages of acceptance right now," Baumstein said, when asked how she felt about the journey before departure.

The endeavour is something no woman has ever accomplished solo. Despite 16 attempts to row solo across the Pacific, only two men have successfully completed the journey – Frenchmen Gerard d'Aboville in 1991 and Emmanuel Coindre in 2005, according to Ocean Rowing Society records.

Baumstein took off on her custom-made 23ft 775-pound boat with 1,200 pounds of freeze-dried food, 180 high-carbohydrate drink supplements and a cache of olive oil that she will consume in hopes of retaining as much weight as possible.

Baumstein, who was recruited as a rower by the University of Wisconsin-Madison before a car accident derailed her athletic career, expects to burn up to 10,000 calories a day and has gained 40 pounds for the trip.

"It's 6,000 miles of an ocean. It's going to get bad sometime, s**t's going to be bad sometimes. Maybe I shouldn't say it like that," Baumstein said.

She has a team that will aid her from land via satellite phone, she will be tracked by GPS, and have an emergency beacon in case of trouble, but there will be no support vessel. She will be rowing up to 16 hours a day in a boat without a motor or sail.

Nonetheless, once Baumstein's boat was undocked and she began rowing away from the marina, she kept a cheerful smile and appeared excited ahead of her expedition.