I once saw something very similar, in January 1998 or '99 at Cook's Beach, after a period of about 10 days of strong easterly winds. There were hundreds of
Glaucus all along the beach, as well as many other pelagic sea-surface creatures, including the two in the top photo. The more elongated one at the bottom is a by-the-wind sailor (
Velella velella) - these are colonial hydrozoans distantly related to Portuguese men o' war (also present at Cook's Beach), though much less toxic. The other is a close relative of
Velella called a blue button (
Porpita porpita), which have a more tropical distribution and are much less commonly seen in NZ. The purple seashells will be species of
Janthina, or violet snails. The commonest in New Zealand is usually
J. violacea, but there's a smaller species,
J. exigua which also comes ashore quite often. Oddly the commonest species that day at Cook's Beach was a much more bulbous snail,
J. globosa, which is normally much scarcer than the other two.
Among the other creatures that came ashore that day were oceanic crabs,
Planes minutus, which cling to floating seaweed and other debris. There were also a couple of other seaweed-dwellers - pale blue isopods (
Idotea metallica) and a small pale nudibranch with two rows of gills down its back, called
Fiona pinnata. And there were lots of juvenile flying fish cast up on the beach as well. Some of these were still swimming along the shore, and a few had washed into the little stream at the end of the beach, which produced the bizarre sight of flying fish swimming alongside whitebait!
This kind of event happens quite rarely in NZ, though
Glaucus occasionally washes up in ones and twos - several iNaturalist records in the last few years. There was a mass stranding of this and associated species reported on iNaturalist about five years ago, which was written up as a short journal entry - link below. The community was dubbed the "Blue Fleet' by Sir Alister Hardy, one of the grand old men of open ocean natural history - a very appropriate name since so many of them are some shade of blue.
https://inaturalist.nz/journal/tangataw ... -otaipango