Visibility is probably the first concern of divers when heading out on a dive. Strong ocean currents on the Irish sea can cause poor visibility along the east coast, however visibility tends to be a lot better on the South and West coasts.
Poor visibility can be caused by…
- Mud – Mud particles can easily become suspended in the water and will quickly reduce visibility -sometimes to zero. Poor visibility caused by mud particles can remain for many hours – especially in choppy seas or strong currents (common around Ireland).
- Sand - Sand does not become suspended so easily, will rarely reduce visibility to nil and will usually clear quite quickly.
- Organic Particles - Bacteria or algal blooms can disturb the visibility in a very dramatic way, the effect can be local and clear quickly, or can be more widespread and last days.
- Salinity Gradients – When waters of different salinity mix, visibility can become very blurry, this can happen near estuaries, caverns or during rain.
- Temperature Gradients – Significant temperature difference between two layers of water can cause an oily effect which quickly clears as the diver passes through the thermocline.
- Ambient Light – Visibility will usually be better on sunny days, and will deteriorate as daylight fades.
- Other Factors - Poor visibility can also be caused by a foggy mask, oxygen toxicity and nitrogen narcosis.
To maximise visibility –
- Dive in calm waters, around stony / sandy shoreline.
- Enquire about local currents.
- Be careful not to kick up mud and sand.
- If you do stir up silt, rise above it and swim against the current.
- Avoid diving mid-tide when currents are strongest.
- Seek local advice.