"At Gilboa we can do just about any training we want," explained Fairfield, Ohio, scuba instructor Roger Van Frank. "Dive shops from all over the Midwest bring students here." The key to Gilboa's popularity is its status as the deepest quarry in the Midwest, plus innovative improvements to facilitate everything from basic Open Water through specialty courses for recreational divers, as well as highly technical commercial and rescue training.

Gilboa Quarry, which takes its name from the nearest recognizable town, is tucked away in the farmlands of northwestern Ohio. Located about two hours south of Toledo or north of Dayton, the main access is via Interstate 75. Scuba training facilities from Pittsburgh, Penn., to Champaign, Ill., and Windsor, Canada, to Cincinnati, Ohio, visit Gilboa regularly.

Like many inland open-water training sites, the present-day Gilboa was developed from an abandoned limestone quarry. Purchased by local resident Dan Diller in 1990, it occupies 14 acres of a 25-acre wooded parcel bordered by a historic millstream. Since then he and his family, all of whom dive, have built eight water entries, including shore walk-ins and convenient wooden platforms with exit stairways. They've installed heated changing rooms, restrooms and outdoor showers, and developed 30 campsites for overnight stays.

The wealth of underwater goodies for use in training, or just having fun, is constantly being expanded. Eight instructional platforms range in depth from 10 to 30 feet/3 to 9 meters. Artificial reef sites include five boats, a school bus and a Volkswagen camper (depth 10 to 55 feet/3 to 17 meters). All are connected by underwater lines to assist in navigation. Stocked walleye, bass and perch abound, and the diver-fed rainbow trout have become Gilboa's equivalent of the Caribbean's yellow snappers. Even the endangered paddlefish can be glimpsed in the far reaches of the quarry.

Gilboa even has its own reef, but instead of coral it's made from PVC. Recently the quarry installed the Diamond Reef SystemTM, a specially designed obstacle course for perfecting buoyancy control. Diamond Reef is both a fun and challenging way to fine-tune one of the most important skills in diving, and a great way to prepare oneself for a trip to some exotic tropical destination. There are also some other underwater features to aid in skills development. One is comprised of two chains of four large tractor tires, each suspended vertically between 10 and 30 feet/3 and 9 meters. The other involves 8-foot/2.4-meter- diameter PVC tubes stacked in grid fashion at 40 to 60 feet/12 to 18 meters.

What makes Gilboa unique is its depth: 137 feet/42 meters. In order to enter the deep end, a dive profile must be filed with Gilboa's on-deck dive supervisor. An unusual underwater feature is the tethered diving bell, from which a semitrailer is suspended at 80 feet/24 meters. While most of the students are recreational divers, the site is frequently utilized by sheriffs' departments and firefighters for rescue training, as well as mixed-gas and other commercial applications.

Typical in these latitudes, the late-summer water temperature reaches into the mid-70s F/mid-20s C at the surface, but declines rapidly with depth. At the bottom the water remains around 40 degrees F/4 degrees C year-round. Visibility ranges from as low as 5 feet/2 meters during the summer algae blooms to 80 feet/24 meters in May and October, averaging 35 feet/11 meters at other times.

Safety is always top priority with the Gilboa staff. Emergency protocols have been thoroughly defined and rehearsed with local Emergency Medical Services providers. Just a few minutes away is an ambulatory care facility, and the recompression chamber in Toledo is a 17-minute flight by helicopter ambulance.

Gilboa Quarry is open for diving every day of the week except Tuesdays. It's open 11 months of the year (closed December). Entrance fees for 1996 are $7 per person for diving, $5 per campsite. For directions and more information call 419-456-3300.