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Glossary - S

SAA Sub Aqua Association. A UK based Diving club.
SAC Surface Air Consumption. The rate of underwater gas consumption converted to an equivalent surface rate, commonly measured in litres per minute. The average id about 25 l/min.
Safety Stop A procedure that calls for a making a safety stop at 6m for 1-3 minutes at the end of every dive for "degassing" purposes.
SALT  Statement of Alternative Level Training
SAR Search and Rescue
Satellite (GPS) An orbiting radio station. A transmitter.
Saturation When a tissue has absorbed all of a given gas at a given depth that it can, it is considered saturated. The amount of dissolved gas a tissue can hold is dependent on the depth at which it is ongassing. The deeper the depth, the greater the amount of ongassing that can occur. As a rule it takes 6 halftimes for a tissue to become 99% saturated.
SC  Surfacing Code
Scope The ratio of length of anchor rode in use to the vertical distance from the bow of the vessel to the bottom of the water. For a RIB this is about 4-6 to 1 for calm weather. More scope is required in storm conditions.
SCR  Semi-closed Circuit Rebreather
SCUBA Self Contained Underwater Breathing Apparatus.
SDC  Skill Development Course (BSAC)
SDI  SCUBA Diving International.
Seamanship All the arts and skills of boat handling, ranging from maintenance and repairs to navigation rope work and knots.
Second Stage The part of the regulator that one breathes from.
SEEDS A BSAC pneumonic that can help to remember the components of a dive briefing. It stands for:
  S=Safety - safety aspects of dive e.g., currents, visibility
  E=Exercise - what the dive plan is
  E=Equipment - special equipment e.g., SMBs
  D=Discipline - leadership, positioning etc
  S=Signals - signals that will be used in the dive
Semi Diurnal Tide These occur in the Atlantic and have two high and two low waters per day.  This is because the geography of the Earth also has an influence on the tidal pattern.
Set Direction, usually applied to tidal movement.
Sextant An instrument, combining telescope and graduated quadrant, used for measuring angular distances, esp. the altitude of sun, moon and stars. Used at sea to determine latitude and longitude.
Shallow water blackout (SWB) Caused by a dramatic reduction in the partial pressure of oxygen during an ascent, leading to hypoxia. As a result, the freediver experiences unconsciousness. There are no indicators to predict the onset of SWB.
Shot Line A rope attached to a heavy weight at one end and a buoy at the other. It is sank onto a wreck or other sea bed feature and used to guide divers.
Sidelights Port (red) and starboard (green) lights. Lights face towards the bow showing an unbroken light, each with an arc of 112.5° from centre line.
SI Surface Interval
SITA  Scuba Industries Trade Association
Skeg Extension of the keel for protection of propeller and rudder.
Slack water Minimum velocity of a tidal current (sometimes abbreviated "slack"). Usually the optimum time to dive wrecks etc.
SMB Surface Marker Buoy.
Snorkel A tube which you can breathe through when floating face-down on the water surface.
Soundings The depth of the seabed recorded below the survey vessel.
SPG Submersible Pressure Gauge - a gauge attached by a hose to a first stage and indicating remaining air pressure in a tank.
Splice Weaving strands of a line to itself or to a second piece of line.
Spring line A pivot line used in docking, undocking, or to prevent the boat from moving forward or astern while made fast to a dock.
Spring tides Spring tides are the biggest tidal range and occur twice a lunar month. They occur at the new and full moon i.e., when the moon and sun are positioned in opposition to each other.
Square Profile Dive A type of dive that involves staying at one particular depth for the entire bottom time and then ascending directly to the surface.
Squally Refers to wind and means gusty, non constant in direction or speed.
Squeeze A pressure-related situation resulting from the failure to equalise on descent. Air-filled cavities such as sinuses, the middle ear, mask and dry-suits are the most commonly affected.
SR  Search & Recovery
SSAC  Scottish Sub Aqua Club
Stab Jacket Stability Jacket. a jacket style, buoyancy control device.
Stage Bottle Extra breathing cylinder carried in addition to the main gas supply. Usually carried on front or side mount clips, but may be attached to a decompression line. These cylinders are designed to provide additional bottom mix gas supply or to provide alternate mixtures for decompression efficiency.
Staged Decompression Decompression performed at specific depths where the diver remains for a period of time to offgas. This is the most common form of decompression for divers. Continuous decompression is generally not available to divers as it requires a very controlled continuous ascent, generally this is only available in a decompression chamber, or on dives that require only a minimum of decompression.
Standing Part The longer part of a line which is fixed during the tying of a knot.
Stand-on-boat One that has right-of-way and should maintain its course and speed.
Starboard As you are facing the front (bow) of a boat the starboard is the right side. Starboard comes from the word Steerboard. Old boats used to have a rudder on the the right-hand-side of the vessel, not the back
Stern The rear end of a vessel.
Stop Dive A dive which requires stops at certain depths for a set period of time. This is done on the final ascent and allows sufficient time to decompress.
Surface Interval The time from leaving the water at the end of one dive to leaving the surface on the next dive. A minimum of one hour is strongly recommended.
Surfacing Code The Code describing the degree of tissue saturation on surfacing from a dive. BSAC use A (no saturation) to G fully saturated).










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