I'm sitting in a tiny, open-air seafood restaurant in Yeonhwari fishing village in Busan, South Korea, waiting for my breakfast.

In the distance, on the rocky shore, a local haenyeo ("sea woman") is picking through her morning's catch.

"She's late," says a fellow patron when she notices me staring. "All the other haenyeo have already finished their diving and delivered their catch."

Like their more famous Jeju Island counterparts, Busan's haenyeo are "mermaids" who support their families by diving for seafood without the use of any particular tools or artificial breathing aids.

The subject of many documentaries, they're a dying breed - an estimated 20,000 haenyeo still work in South Korea - due to the intense physical difficulties of the job.

While most haenyeo usually dive about five meters and stay underwater for 30-second intervals, many are capable of diving as deep as 20 meters and staying underwater for as long as two minutes.

Read - Mermaids, abalone and a very local breakfast in Busan