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Typical Underwater Line System Used By North Carolina Wreck Diving Charter Boats
The techniques used for entries and exits from dive boats vary greatly from region to region. This underwater line system, used by many North Carolina charter boats, may be the best method for a variety of environments. It simplifies the entry and exit procedures, reduces diver stress and disorientation related to marginal sea conditions, encourages a slow controlled ascent through the last portion of the water column and provides and excellent platform for safety stops and stage decompression.
The system features two vertical lines, one mid ships and one aft, with a 20 to 30 pound lead weight on the end of each line. Between these vertical lines at a depth of about 15 FSW a horizontal line is attached. From the foremost vertical line a line runs forward to a sliding weight attached to the anchor line. The length of the line leading to the angle is such that the sliding weight will rest at a depth of about 30 to 40 FSW (dependent upon scope). The system is duplicated on both the port and starboard sides of the charter boat.
When entering divers normally make a Giant Stride entry from mid ships with their BCDs totally deflated. As they begin to sink beneath the surface they turn to the vertical down line a follow it to the 15 FSW level. The members of each dive team meet at the horizontal line, do a quick bubble check and use the lines to pull themselves to the anchor line if any current is present. They complete their descent along the anchor line to the wreck or reef below.
This entry method has a number of advantages. As nearly any dive charter boat crew member can attest, most problems occur at the surface. These problems are normally related to anxiety created by the diver being bounced around by waves or overexertion trying to swim against waves and/or current to reach the anchor line for descent. By getting the diver beneath the waves quickly any anxiety caused by surface waves, usually a feeling of being out of control, is eliminated. Additionally, the lines provide an easy method to move forward to the anchor line for descent, reducing overexertion problems.
At the end of the dive the scuba divers make a normal ascent up the anchor line until they reach the slide weight. They then follow the line, on a gradual slope, to the 15 FSW horizontal line for a safety-stop or to compete their decompression obligation. Because the connecting line between the anchor line and the foremost horizontal line is on an angle, the diver is forced to slow their ascent rate and get their buoyancy under control. This provides some obvious physiological advantages for the diver. The line system also provides a convenient platform for conducting safety-stops or stage decompression, eliminating the competition for a single point of depth on the anchor line by all ascending divers.
When the divers have completed their safety or decompression stop and are ready to ascend to the surface they simply swim up a few feet behind the boat, grasp the floating current line and exit via a fins-on boarding ladder. When using a fins-on ladder the diver should grasp the highest rung they can reach, pull themselves forward onto the ladder and avoid looking down. A diver taking hold of a bottom rung on the ladder could find them self at the end of a violently moving lever, resulting in a less than pleasant ride if any surface wave action is present. With mask, fins and regulator in place the diver climbs the ladder to the swim platform where a crew member helps them remove their fins.
Obviously the underwater line system used by many North Carolina charter boats offers a lot of advantages. Stress and anxiety caused by wave action on the surface is eliminated, the exertion of reaching the anchor line is minimized, it forces a slow ascent through the shallowest portion of the water column and provides a comfortable platform for executing safety-stops and stage decompression. Perhaps, with time, this system will become widely used outside of the Mid-Atlantic region.
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