– Adjustment of the gas content in buoyancy compensator and dry suit to achieve appropriate buoyancy Trim control – Control of attitude in the water to suit the circumstances. Depth monitoring and control – Observation of current depth and ensuring it is appropriate Standard dive activities Mask clearing and demisting – Discharge of water from the mask, and rinsing off condensation from the inner surface Maneuvering and mobility – Self-propulsion in the water column Monitoring decompression status – Keeping track of personal decompression obligation Monitoring breathing gas supply – Ensuring that the remaining gas supply is sufficient to complete the dive safely Balancing cylinder usage – ensuring that enough gas to safely finish the dive remains if any one cylinder loses all remaining gas. Use of auxiliary equipment – Useful equipment, not needed on all dives. Towing a Deployment of a Planned diving activities - These are mostly considered underwater work, with a few exceptions and borderline cases. - This is generally considered to be a diving skill, not a work skill. Laying, marking, following and retrieving distance lines (guide lines). – Safety critical procedures in an overhead environment. – In professional diving these may be considered diving procedures or work procedures. Ascent – A generally consistent decrease in depth until the surface is reached. Decompression – The reduction in ambient pressure experienced during ascent from depth, and the process of elimination of dissolved inert gases from the diver's body tissues. No-stop diving – Diving which limits tissue inert gas concentrations to those which allow acceptably safe surfacing without decompression stops Repetitive diving – Diving again while some tissues have not reached equilibrium with surface saturation. Staged decompression - Decompression at fixed depth intervals, a practise which allows use of decompression tables. Gas switching - Changing between breathing gases during a dive to a gas suited to the current depth, to limit oxygen toxicity or nitrogen narcosis, or to accelerate decompression Management of multiple cylinders – Managing additional cylinders with different gas mixtures. Accelerated decompression – Use of oxygen enriched gas mixtures to accelerate inert gas elimination. Oxygen decompression – Use of pure oxygen to accelerate inert gas elimination. Monitoring decompression using a planned schedule, depth measurement and elapsed time. Monitoring decompression using a Surfacing – The final stage of ascent Return to exit point – Getting from the position of surfacing to a place where the diver can safely