When the Gen. Hoyt S. Vandenberg is sunk five miles off of Key West later this spring as an artificial reef, the impact on the Southernmost City's dive shop community is expected to be dramatic.

How far north that impact stretches is still anyone's guess, but dive shops in Marathon are hoping for some sort of bump.

At Hall's International Career Institute and Diving Center in Marathon, the Vandenberg will provide a new opportunity to train potential instructors and hopefully catch a wave of increased scuba diver activity funneling up the Keys.

"[The Vandenberg] is very diver accessible," said Bill Anderson of Hall's. He noted that his shop had just ordered some new re-breathers to use on the wreck. "I hope I can get off on sink day to watch it go down."

Down the road at Tilden's Dive Center, Scott Fryer said the addition of the Vandenberg in Key West will create sort of a "wreck alley" of dive sites throughout the Keys.

"I think it is going to be great," he said.

Brent McKee of Innerspace Dive Center in Big Pine Key agreed, noting that there are several other wrecks in the Lower and Middle Keys that are popular with divers.

"Nobody is going to want to dive [the Vandenberg] four days in a row," McKee said.

Fryer said that when the Spiegel Grove was sunk off of Key Largo in 2002, it create a buzz in the diving community, and he expects the same thing to happen with the Vandenberg.

"It got a lot of attention right off the bat," Fryer said.

Marathon has its own popular wreck site, the Thunderbolt, an 85-foot cable laying boat sunk in 1987. It is located about five miles off shore. Although Key West tends to get more national attention for this type of event, the overflow could make those in the Middle Keys happy with some additional customers.

"They have to come through here," Fryer said of Marathon.

Greater marathon Chamber of Commerce Executive Director Daniel Samess said that while the Vandenberg will provide another attraction for the Keys, he was not sold on it being a boom for Marathon

"I think it will have a minimal economic impact on Marathon," he said.

A new popular wreck will also mean a slew of inexperienced or rusty divers returning to the water. Terms such as neutral buoyancy, safety stop and bottom time have lost their significance, but operators of local dive shops say that is all about to change.

Dive shop operators are preparing new protocols for the wreck dive. Most are offering more refresher courses and more advanced level and Nitrox classes for the adventurous and experienced divers who want to see the most of the former military ship.

"It's time for everybody to knock the dust off their equipment and get into the shops to get it serviced, because you don't want to miss this summer," said Capt. Joe Weatherby, who initiated the reef project with Capt. Sheri Lohr more than a decade ago.

Jessica Opie of Subtropic Dive Center said the shop has been getting calls about refresher courses.

"We recommend the $65 refresher courses for anyone who has not been diving in the past two years," she said.

The height of the ship will make it accessible to divers of all levels. The top of the ship will be in 40 feet of water, while the keel will be on the ocean floor at 140 feet.

The challenging deep dive has prompted many people to upgrade their diving certification and explore Nitrox, or mixed-gas diving, to allow for more bottom time, said Capt. Chris Norwood, owner of Florida Straits Diving Inc., and president of Artificial Reefs of the Keys, the group that initiated the reef project under Lohr and Weatherby.

The amount of experience that divers can prove with their logbook will be the key in determining the depth they achieve on Dive Key West boats, Bob Holston, co-owner of Dive Key West said.

"They'll have to present a logbook to dive with us, and all dives will be guided by one instructor per six divers," he said, adding that diver safety is the ultimate priority.

Southpoint Divers also is working on its new dive programs, and finalizing what levels of wreck penetration will be possible.

"Our preliminary outline is that open water divers will be able to go with a guide with minimal penetration, and advanced divers can go with their own teams, but no penetrating the wreck," said Eric Schaaf, general manager of Southpoint. "Advanced divers with documented training and experience in overhead environments such as cavern, cave, ice or wrecks, and with the proper tools and equipment can explore on their own."

"This artificial reef will be perfect for everything from fish counts to photography, and snorkeling to tech diving," Weatherby said Monday.

For continuous weather and position updates, go to http://www.srh.noaa.gov/key/ and click on the Vandenberg icon.

mbolen@keysnews.com