Ta-Wr

Tangle Nets/Gill Nets

Indiscriminate fishing, particularly on wreck sites, with difficult-to-see monofilament netting, is a real hazard around the British coast. Experiments have shown that the average diver's knife is very ineffective should the diver become entangled. A line cutter or a curved blade 'dinghy' knife, with a blunt end, are probably the most effective for this purpose and need to be worn on the arm. A knife with a sharp point could lead to a diver stabbing himself when in difficulties. Small shears or scissors are recommended as an effective tool for cutting netting.

Once caught in netting, it is advisable to partially inflate your BCD, so you rise inside the net, putting it under tension and making it easier to cut. The positive buoyancy will also help to 'tear' you away. If your buddy is free of the netting they may be advised to cut you out, still enmeshed, and worry about completing the job on the surface.

Remember to think, breath, and act. Excessive movement may increase entanglement so look first and consider your options. It may also best to rely on your buddy to cut you free.

Theoretical Depth at Altitude Chart

Theoretical Depth at Altitude Chart

Tides

The success of any sea dive depends on accurate, local, tidal predictions for the dive site you wish to visit. Admiralty charts give accurate large scale predictions and should be used in conjunction with the relevant local tide tables. Tidal Stream Atlases are also useful and are available for the UK and many other sea areas throughout the World.

Trimix

Trimix is a mixture of three gases, Oxygen, Helium and Nitrogen in various percentages.

Also see Mixed Gas.

VHF Radio

VHF (Very High Frequency) radios are a valuable aid to safety at sea and, together with suitable waterproof housings, are frequently used in small boats. Radios should be licensed and, under normal circumstances, should only be used by, or under the supervision of, someone who holds an appropriate Certificate of Competence. It is an offense to use Marine VHF radio from the land, (unless it is a registered land station) so your shore party is not allowed to use one.

Weather

Acquiring an accurate weather forecast for your dive site can save a lot of unnecessary traveling expense and can mean the difference between a controlled successful dive and a risky experience.

The NOAA's National Weather Service provides weather forecast with easy-to-understand symbols. Some daily newspapers carry a good forecast with weather map, and the Maritime and Coastguard Agency always has up-to-date forecasts. RAF stations have a meteorological station and are usually very helpful.

If unexpected weather, especially thunderstorms, arises, it is best to abandon the dive and head for safety.

Weightbelts/Integrated Weight Systems

Weightbelts or integrated weight systems, when used, should always be fitted with a reliable quick release and fitted so that they will always fall clear of other equipment when released. You should be practiced in releasing your weights and should also make sure that your buddy is well briefed and fully familiar with your release mechanism. If the buckle is of the same type as on the cylinder harness, it is wise to wear it so that it operates in the opposite direction.

Wreck Diving

Wreck diving is one of the most popular forms of diving and requires extra safety precautions if divers venture inside the wreck. Many steel wrecks are in a dangerous state of decay, and loose overhead objects or steel plates are a real hazard. Never venture deep inside a wreck without ensuring your route to clear water is certain, and use a reel and line secured to the outside of the wreck to mark your return route. Avoid excessive finning inside a wreck as sediment stirred up is very slow to settle, due to lack of tidal flow. Always allow an adequate reserve of air at the end of your dive and never run down your air supply by attempting to remove an artifact. Never try to lift heavy objects from wrecks using your BCD and/or drysuit. Underwater ordnance can be very unstable and should not be recovered. It is a criminal offense to be in possession of explosives without the relevant licenses.

Also see Diver's Code of Conduct - Wrecks.