“It all smells a bit fishy around here! Wondering what the smell is today? Seems to be some kind of jellyfish? Washed up on our beautiful beach as far as the eye can see (and the nose can smell).” (From the Waikanae Beach Residents Association Facebook page)

Not aliens but Velella.  It’s been reported all along the North Island west coast from Makara to the Taranaki.