All North Shore beaches were reopened yesterday after warning signs were posted Wednesday following a shark attack.

Lifeguards will continue to monitor beaches from Laniakea to Waimea Bay, officials said, particularly beaches that do not have lifeguard stands and are checked by mobile units.

Warning signs were posted Wednesday afternoon after a 26-year-old diver suffered cuts to his left forearm while free-diving at a surf spot known as Marijuanas near Chun's Reef.

Friends identified him as Ronald Deguilmo of Waipi'o. He was diving with two friends in about 25 feet of water when a shark bit his arm, friends said. Deguilmo told friends that he hit the shark with the butt of his spear gun and that the shark swam away.

Deguilmo was taken to Wahiawa General Hospital.