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.