Montesha Kekana went missing from her home in Iraq informal settlement near Saldanha on Thursday at 6pm, said Captain Bernadine Steyn.
She was seen walking with a 32-year-old man who was being questioned by police.
Kekana was wearing a pink top and maroon trousers.
Steyn said police had deployed their diving unit to begin a search of Tabak Bay.
Sapa
Rebekah Kendal counts the banana peels between SA and Robert Mugabe's failed Zimbabwe.
From funny moments to serious stuff, iafrica.com brings you the week's best pictures.
Do you need a laugh? Then check out our offbeat stories from around the world...