On our Sunday walk along Piha beach yesterday, we encountered a good number of these bluebottles (Portuguese-Man-o-War, physalia physalis). The tide was way out, and they were left behind. These jellyfish-like creatures normally float on the surface of the ocean, moving as the wind catches in their inflatable air bladder and sail. They have long thread-like tentacles which dangle in the water and can inflict unpleasant stings. The bluebottle in the picture measured about 12cm.
In the background is of course Lion Rock, which featured on this blog before.