By: Joe Rojas

Cartography By: Curt Bowen
            (extrapolated from the original map created by:)
Greg Schmoll•Mark Hermerding•Ralph Walter•Bob Foster


Points of Interest

A. Entrance restriction:
    2 1/2’ high by 10’ wide, high flow.

B. Upper level of cave is a standard 10 foot high and 50 to 100 feet wide bed plane. Lots of silt and low flow.

C. Unique horizontal arches located here in the passage.

D. Parallel passages all lead to the “Pit”.

E.  “The Balcony"

F.        “The Pit” Over 100 feet in diameter, the pit drops straight from 50’ at its ceiling to 285’.

G.        Up-line used to attach deco cylinders at various depths.

H. The “Deep Restriction” Just large enough to navigate with a scooter, extremely high flow.

I. End of line at a depth of over 350 feet. The passage continues at a 30 degree slope downwards with a tunnel size of 10’ in diameter.

Bubbling springs, sparkling rivers, and forested hills highlight the beautiful state of Missouri. Some of  these springs contain aquatic cave systems that are unique to dive, however Missouri has never been recognized as a quality diving destination and, as a result, Missouri caves are rarely visited or explored. Roubidoux is the most popular of the Missouri caves, but even the yearly attendance at this choice spring is only equal to a single day at some of the more popular Florida caves. The Missouri cave systems of Roubidoux, Meramec, Blue, Bennett Cave (Devil’s Well), and Cannonball, are less than 2 hours from St. Louis. The extent of Missouri springs have not yet been reached and as exploration continues, local divers are confident that there are more caves within the springs to be discovered. The jewel of the Missouri caves is Cannonball. It is a unique system due to its location, depth, and difficulty in diving.

Cannonball cave, formerly known as Davidson’s Blue Hole Outflow, created a hillside pool and a small creek that fed into the St Francis River 100 yards to the west. It had a flow of approximately 31.7 million gallons per day, which is small in comparison to some of the other Missouri springs. In 1939, the U.S. Army corps of engineers built a public flood control reservoir for the St. Francis River and all its tributaries. The dammed river flooded over the spring’s mouth and surrounding area, creating a reservoir called Lake Wappapello. The entrance to the spring now lies at an average depth of 28 feet depending on the dam’s water level. On a calm day it isn’t uncommon to see the boil that is created by the turbulent spring water in the murky-still reservoir.

A problem with diving Cannonball is that the nearest parking area (within a few hundred feet of the spring) is on top of a hill that is over 100 feet above the water’s edge with a 40-60 degree decline. The hill is not bad going down as long as you are taking it slow; the problem is walking back up with doubles, stage tanks, and scooters. It is definitely a test of physical ability and can put divers at risk of the bends after doing a 300-foot dive. Fortunately there are alternatives to trekking the hill. One is a boat landing to the west of the spring, it is possible to scooter to with an estimated distance of 500 to 800 feet. The best choice is to come by boat, mooring it right off the spring with a designated person tending the boat and assisting the divers on entry and exit. It is important to bring a dive flag, as this area is also favored by fisherman. As you enter the water, the river temperature can vary from high 70’s to low 40’s depending on the season. It takes time to find the cave entrance since the surrounding water has zero visibility, but once the spring outflow is discovered, the visibility becomes remarkably clear.

On a recent visit to Cannonball with my dive partner Greg Guzman, the river temperature was around 55 degrees Fahrenheit, and spring temperature was 57 degrees Fahrenheit. We found the entrance at 26 feet. A resident catfish almost 3 feet in length was found guarding the opening of the cave. The entrance has a restriction that is 30 inches in height at it’s largest point and an overall width of 10 feet. The restriction continues past the opening with a length of 10 to 12 feet that finally opens up to the system. By following the main line you first make your way around a large boulder, then the line makes a 60-degree northeast turn. You will notice the dark walls and silt floors, which marks this cave’s difference from popular Florida cave systems. The first 50 feet is a step over of rocks that have fallen from the ceiling. The cave continues in a northeasterly direction at a depth of 40-45 feet, there are parallel passages on the right of the main line which are reachable with a gap or jump reel. These side tunnels lead back to the main tunnel and make for an enjoyable dive, being careful of the low ceilings and the buildup of silt. The visibility fluctuates in the system from 5 feet to 60 feet during the year depending on rainfall and lake height.

This is truly one of the most beautiful cave systems in Missouri. There are unusual rock formations at approximately 500 feet, where natural stone bridges divide the cave horizontally. Passage can be made above or below them. At a distance of 750 feet you reach a room that drops to a black abyss. The room has a width of 150 feet at the top and an average width of 60 to 80 feet further down the tube. In the drop off there is a dropline that is being held up by a truck innertube so that divers can place their stage tanks at specific depths. On the way down we dropped our decompression gases off at 70, 120, and 220 feet. Our back gas was mixed for a 350 foot maximum operating depth (MOD). We had two additional stage tanks, one with the MOD of 350 feet and a second stage tank with a MOD of 400 feet to leave for the next dive. The large room drops to a horizontal restriction at a depth of 285 feet. With the recent absence of rain in the area it was fairly easy to maneuver by pulling along the bottom or using a scooter on full throttle to bypass the high flow in the restriction. At times, strong water flow (dictated by the season and recent rainfall) can make it very difficult to navigate this tight restriction. After the restriction, the ceiling height drops with a clay bottom to a depth of 315 feet.  200 feet past the restriction the cave begins to open up and has another drop off that slopes slowly to an estimated 350 feet depending on water levels. Unfortunately most dive computers stop at 328 feet, which made a problem determining the cave depth. The end of the line is approximately 650 feet past the restriction, in which there is more of the cave to be explored in the future. We stopped just shy of the last tie off and turned on the available time that we set for ourselves.

            The problem with dives in Cannonball that require multiple gas decompression is getting the stage tanks in the first restriction. It is difficult enough just getting through with a set of doubles, but with 3-6 additional tanks it can be very time consuming. This is why having a setup dive is crucial. Another difficult circumstance to overcome is the long decompression in the 55-degree water; our dive had a total runtime of 3 hours and 20 minutes. Special steps must be taken in preparation and training for these dives.

            In Missouri cave diving there is endless enjoyment and challenge, from the diver who wants to stay above 60 feet to the diver who desires to go past 300. I find myself lucky to have been able to experience these caves and find them an interesting change from the caves of Florida and Mexico.