the 'sand' is very silty all along that part of the coast ie. soil washed down by the rivers. therefore shore wave action causes the 'mud' to disperse thru the water column. that's the brown stain.

In 2026, if you notice the water at Palm Cove (near Cairns, Australia) looking brown or murky, it is usually due to natural seasonal factors rather than pollution. The most common cause is sediment runoff from the nearby Barron and Mulgrave Rivers, particularly after heavy tropical rainfall which is frequent in Far North Queensland. This rain carries nutrient-rich soil and tannins from the rainforest into the Coral Sea. Another common 2026 phenomenon is Trichodesmium (Sea Sawdust), a type of blue-green algae that forms large brown or yellowish "slicks" on the surface of the water during calm, warm weather. While it can look unappealing and occasionally smell like decomposing vegetation, it is a natural part of the marine ecosystem and is generally harmless to swimmers. However, during the "stinger season" (November to May), a brown or cloudy sea can make it harder to spot jellyfish, so swimmers are always advised to stay within the stinger nets and wear protective lycra suits regardless of the water's clarity.