6-foot seas without danger from movement of the barge. The hatchway also affords tlie 

 diver an excellent means of boarding and leaving the barge deck without damage to his 

 equipment and without interfering with other workers on the deck. 



The barge was held in position by a four-point mooring system from each corner of the 

 barge. A separate Une extends from the underwater staging to the bottom station for easy 

 diver movement from the barge. 



2. Bottom Rope Support System 



A diver in fuU scuba gear can swim for a short time at a maximum of 50 centimeters per 

 second. Since current velocities of 75 to 100 centimeters per second were common, and 

 velocities up to 250 centimeters per second were possible, the diver needed a support 

 system. A series of aluminum pipes, 125 centimeters long and 3 centimeters in diameter, 

 were placed about 75 centimeters deep and 10 meters apart in a line in the direction of 

 current flow. A 3/8-inch nylon rope was run from pipe to pipe. A rope grid system was 

 constructed when two rows of pipes were used. Fifty to seventy meters of line were thus 

 constructed with a 10-meter traUing rope at the downcurrent end of the system. The line 

 from the barge was attached at the upcurrent end of the system. A small dinghy, anchored 

 50 meters downcurrent of the last pipe, acted as an emergency station if a diver was swept 

 past the last pipe. The diver is propelled down the rope system by the current, using the 

 rope as a guide. He moves hand-over-hand along the rope in a upcurrent direction. The pipes 

 provide convenient resting points, and, if an elbow is hooked around the pipe, a hand is free 

 for other work. Figures 6 and 7 illustrate the complete barge-rope support system. 



The rope support system enabled the crew to work reasonably well in current velocities 

 up to 100 centimeters per second and with difficulty in velocities up to 150 centimeters per 

 second. Moving along the bottom is not difficult at this increased velocity, but fluid drag 

 tends to loosen diving equipment (e.g., face masks) and hand-held gear can be torn from the 

 diver's grasp. A 1.75-inch -diameter rope is recommended to reduce hand fatigue. 



3. The Greer Compass Case 



An accurate device to take underwater measurements of sUpface azimuths of bed forms 

 was achieved by mounting a Brunton compass in a waterproof housing. The case, modified 

 from a design by Sharon Greer, is constructed of 0.5-inch plexiglass. It is a simple and 

 inexpensive means of converting a Brunton compass into a useful underwater tool. (Figure 8A.) 



A clear box, with outside measurements of 1.35- by 6.6- by 3.4-inches, was machined to 

 accept an 0-ring seal and fitted to a 13- by 4.5-inch plate to form a watertight compass 

 housing. Six 0.5- by 0.7- by 0.7-inch blocks were machined to accept 0.5- by 0.6-inch wing 

 nuts. These blocks were fused to the front housing unit at regular intervals (corresponding 

 to six holes in the backplate) to maintain a watertight seal. 



A 2.8- by 2.8- by 0.5-inch plexiglass block was centered 8 inches from one end and fused 

 to the backplate. The block supports the compass cover in an open position and helps 

 steady the compass. A hole 2 inches in diameter and centered 5 inches from the same end, 

 was cut next to this block for easy access to the clinometer arm. A cyUnder was then 

 machined to an inside diameter of 2.5 inches and placed over the hole in the backplate, and 

 a 3-inch plate was fused to the cylinder. A 3/8-inch hole was drilled to accept an IkeUte 

 camera control. (Figure 8B.) The shaft on the camera control was cut to 2 inches and joined 

 to the cHnometer arm by an adapter machined to fit over the arm. Finally, a 1/4-inch 

 neoprene gasket was fitted over both the support block and the hole in the backplate to 

 cushion the compass and to help hold it in place. 



