The thrill of viewing sharks up close in waters off the North Shore through Plexiglas and the bars of a metal cage has attracted many curious customers.

But a proposed rival operation in seas south of Oahu has drawn mixed reviews.

Iolani Lewis, operator of the Snoopy V, docked at Koko Marina next to Kona Brewing Co., plans to launch a shark-encounter tour south of Maunalua Bay.

“;We're not in support of the company opening up there because of the population there and the water usage there and also simply because we don't know what their procedures are going to be,”; said Stefanie Brendl, owner of Hawaii Shark Encounters, which operates out of Haleiwa Harbor. “;Three miles out from Hawaii Kai is different from being three miles out from the North Shore.”;

Brendl, who has been operating her business since 2003, focuses on shark conservation and educates patrons on why sharks are needed to maintain a balance of the ocean's ecosystem.

The North Shore tours take advantage of an already established population of Galapagos and sandbar sharks, relatively harmless species that are attracted to boats recovering crab traps. Commercial fishermen have set up crab traps off Haleiwa for at least 40 years.

The sharks habituate to the noise of the boats and congregate near the vessels as fishermen empty their traps of old bait, said shark expert John Naughton.

Naughton — who retired last year after 40 years as a biologist with the National Marine Fisheries Service and still does consulting work involving sharks — said he is concerned with the amount of palu, or chum, the South Shore operator will need. The seas off Maunalua Bay have no natural concentration of sharks.

“;They were taking advantage of a situation set up by commercial fishermen,”; he said of the North Shore operations. “;It didn't require them to throw a lot of palu or chum in the water.”;

South of Maunalua Bay, attracting sharks will require a concentrated blood trail, which could be problematic, he said.

“;It's going to set up a situation where you get larger species of sharks coming in, like tigers and possibly white sharks.”;

Tiger sharks, which are the size of humans, are behind most attacks on humans in Hawaii waters.

Naughton is also concerned with behavioral changes of near-shore sharks and a proliferation of shark-encounter operations around the islands. So far, Hawaii Shark Encounters and North Shore Shark Adventures, both based in Haleiwa, are the only two operations statewide.

They operate three miles offshore, which is outside of the state's jurisdiction, in an effort to avoid near-shore recreation activity.

Kim Holland, a researcher with the University of Hawaii's Institute of Marine Biology, said he supports the proposed operation.

“;If we can generate income and jobs from use of the ocean that don't involve killing things or harvesting animals, I'm personally in favor of it,”; he said. Holland is involved in several different sharks research projects, one of which involves a collaboration with North Shore Shark Adventures, the first shark encounter tour established in Hawaii nine years ago. It is owned by Joe Pavsek who, like Brendl, opposes the Maunalua Bay operation.

Based on his study, Holland said there is no evidence sharks visiting the tour site off of Haleiwa are coming close to shore, but that could differ from one site to the next.

Lewis, who leases the Snoopy V, could not be reached for comment.