These sludges on the beach are naturally occuring "blooms" of surf diatoms (not caused by pollution). There is a bit more detail on recognizing them over on the VBOP site
This 130 megapixel photosynth is based on 37 photo. It was taken handheld just south of Beach One at venus bay and illustrates the recent erosion at the back of the beach. The photosythyn was created by Microsoft ICE (Image Composite Editor).