Because Galway disposes of a part of its waste water in the bay the amount of nutriments, particularly for algae has increased in recent years. This has boosted the growth of slipperslimy green hair weeds. But slippery has many faces.
When there is a storm froth flakes are blown over the rocks in great numbers. When these have dried up you don’t see them anymore, but they still are super slippery, especially when you have wet soles. And then there is this brown deposit that is mostly caused by slowly returning water. When every thing is wet from the rain it is difficult to see the difference between reliable and slippery. Plenty of reasons to be extra careful about where you walk. Best is to step on top of your feet and seek support for your hands. When it is dry rock walking is so much safer and a lot more fun.