A Haleiwa woman was seriously injured Sunday when she was bit by a shark on Oahu's North Shore. The 54-year-old woman -- identified by friends as Marjorie Mariano -- was surfing off of Laniakea Beach about 6 p.m. when she was bitten in the thigh by a large shark. Other surfers helped bring her ashore, where she was treated by emergency crews. She was taken to a hospital, where she's recovering. Ocean Safety lifeguards assessed the beach on Monday morning, and posted shark warning signs. The beach is open.