Swimmers and divers off Windward O'ahu are on notice that if they see a fluorescent dive buoy moving through the water on its own, it may be attached to a tiger shark.

The buoy, along with a spear gun, belongs to Kailua resident Bert Wissig, who said he had a close encounter with an 8- to 10-foot shark yesterday afternoon off Lanikai Beach. Wissig, 42, wasn't harmed, but he did lose his gear, which was valued at $300.

Wissig said he was wrapping up an afternoon of spearfishing when he spotted something "gray and very large" in the water. He realized it was a shark and noticed it had a line tangled in its mouth.

The line, Wissig said, was attached to his dive buoy, which was attached to his spear gun.

"After it circled me a couple of times it basically took off and there was no way I could hold on to my gun anymore," he said. "It just took my whole rig and took off. So it's probably still swimming around with that buoy attached to the line that's entangled in its mouth."

Wissig kept an eye on the bright orange buoy as it headed toward Kailua Beach, but he lost sight of it in the surf.

Wissig swam to shore and drove to Kailua Beach to report the incident.

He said he was concerned because he's never seen a shark off Lanikai in the nearly two years that he's dived there and that the shark was heading toward crowded Kailua Beach.

But he said no one answered the phones at the Department of Land and Natural Resources and that lifeguards didn't appear to believe his story. He had asked them to post signs warning of the shark.

"To them it was an unconfirmed sighting and they don't act on an unconfirmed sighting," Wissig said.

Bryan Cheplic, spokesman for the city Department of Emergency Services, said lifeguards checked the area twice but didn't see a shark or the buoy.

"Unless we see something, we won't do anything because the last thing we want to do is create mass hysteria," Cheplic said.

Wissig said he's also concerned about the welfare of the shark, which was dragging his gun and buoy like in a scene out of the movie "Jaws."

"The buoy might not be the biggest but over time I'm sure that it can put a lot of stress on that fish and it might not come out too healthy," he said. "Maybe this shark can bite through it over time, I don't know."

Despite this experience, Wissig said, he plans to get new equipment and he will return to his favorite fishing spot.

"I figure, statistically speaking, this was probably my encounter for the next 10 years. I'm probably safe now," he said.

"I didn't really have the feeling that it was after me at all," Wissig added. "It might have been, I don't know, and it might have been distracted once it got entangled in the line. But even when it was swimming around me I don't think it ever really had the intention of going after me."

Reach Curtis Lum at culum@honoluluadvertiser.com.