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Cannonball Cave
 Greenville, MO 63944
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Max Depth: Over 150ft/46m
Average Viz: 26-30ft/8-9m
Bottom Composition: Clay/Muck
Aquatic Life: None
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Rating: 4.00 by 1 divers
Spring: 56-60°F/13-16°C
Summer: 56-60°F/13-16°C
Fall: 56-60°F/13-16°C
Winter: 56-60°F/13-16°C
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Cannonball Cave is a fresh water dive site, located in Greenville, MO 63944. This dive site has an average rating of 4.00 out of 5 from 1 scuba divers. The maximum depth is over 150ft/46m. The average visibility is 26-30ft/8-9m.
Cannonball cave is a cave dive for those properally trained.
Locals called the spring, Davidson Spring. It has also been called Davidson’s Blue Spring (cf. pp. 60-61 of book "The Large Springs of Missouri"). The name came from a family who homesteaded near the spring. Their cabins were still standing until just a few years ago uphill and slightly north of the spring.
Before the construction of the dam by the Corps of Engineers the spring issued from the base of a rock cliff and then flowed about 300 feet to the St. Francis River. Measurements taken from 1932 to 1939 showed it with flows of between 27 and 51 million gallons per day. John Davis, a local, has a great deal of history and photos of the spring and the building of the lake (if you are interested in contacting him I can get you a phone number and address).
Divers began calling it Cannonball cave because of an old round-shot cannonball that was in the mouth of the entrance. It had apparently been used as a boat anchor and had broken off and fallen at the base of the cliff where the cave entrance was.
There is little viable cavern zone. The entrance is a restriction c. 2.5 feet high and 12 to 15 feet wide. Only the center portion can be used by back mounted divers. After about 15 feet the cave opens up into a large tunnel which leads to a pit a little over 700 feet from the entrance. Along the way there are several jumps, but each leads back to the main tunnel. There is also a short jump off of the pit itself.
There are absolutely stunning clay formations throughout the caveespecially in the upper tunnels. There are some instances where there are 15 or more layers of colored clay (black, orange, white, gray one after the other and repeating themselves). I haven’t seen the like anywhere elsenot either in Missouri or Florida.
The pit drops sharply down through a series of concentric rings to the mouth of a restriction at 280 feet. Larry Hodges and I put a 1/2" rope through this restriction to make getting through it possible without expending copious amounts of gas. The flow can be rather mild in the fall, but for a good part of the year it can be like trying to swim into a fire hydrant. I was attempting to get through the restriction, before we installed the rope, some years ago when the flow was fierce and I saw Elvis frog kicking in front of meand he was wearing a thong bikini bottomit wasn’t a pretty sight.
Beyond this restriction is the "Mud Room". It is a wide, low silty room c. 30 feet in width and 3 to 5 feet high. We spent several dives exploring this room for leads, but there were none. There is a slight incline as you swim toward the center of the room, then it begins to drop and opens up into a large tunnel at a depth of 277 feet.
This "Deep Tunnel" is 10 to 15 feet in height and width and travels for a little more than 250 feet where there is a third restriction at a depth of 365 feet. The cave honeycombs at this point and once through the restriction you cannot go more than 20 to 25 feet. There is no flow at this point and it is impossible to crawl through the restriction without reducing the viz to zero.
Where the Deep Tunnel begins there is another tunnel off to the south (left as you are facing the Deep Tunnel) which I explored for about 50 feet a few years ago. I think this is where the flow is coming from and it is at a depth of c. 270 to 280 feet. You can reach this part of the cave swimming in less than 30 minutes. I have made it to the end of the Deep Tunnel in 32 minutes (when I was not exploring or laying line).
The spring water temp doesn’t vary all that much c. 55 to 57 f. on the guages I have. The lake water goes from 80 f. something in the summer to 40 f. something in the winter. The short diving season (at least the diving season with good viz and low flow), hinders exploration a great degree. Dive teams like the OCDA (Ozark Cave Diving Alliance), have the best resources and skills for pushing this system. Skilled team work will take you further, and with greater safety, than either single divers or a few divers pushing it on their own.