N early four months ago, Catherine Breed, a 33-year-old from the San Francisco Bay Area, set out to become the first person to swim the entire coastline of California – from its northern-most tip to the border with Mexico. She and her support team prepared for encounters with sharks and storms. They hadn’t anticipated completing the marathon swim during a year of historic super El Niño weather .

But after dodging hurricanes, wildlife and 8ft waves in an unusually volatile Pacific Ocean, Breed finally celebrated the end of her journey on a beach in San Diego on Monday.

Breed joins a group of elite ultra-endurance swimmers who continue to set new records for long-distance swims, including swimming the entire coastlines of Ireland and Iceland and one side of New Zealand’s North Island – all journeys of close to 1,000 miles (1,600km).

Breed spoke to the Guardian this week about living onboard the Catalyst, the sailboat that accompanied her, her physical and mental preparations for her 111-day swim, and what…