Lifeguards closed off part of a popular Hawaii beach after spotting a large, aggressive shark, which is bad news for swimmers but a sign the warning system is working as intended.

• An 8-to-10-foot shark was seen acting aggressively near Maili Beach Park in Waianae.
• Lifeguards posted warning signs at the beach Tuesday afternoon to keep swimmers out of the water.
• Officials are telling beachgoers to check with lifeguards for the latest conditions before swimming.

Outlook: Warning signs will likely stay up until lifeguards confirm the shark has left the area.