Hormosira banksii, (also known as Neptune's necklace, Neptune's pearls, sea grapes, or bubbleweed) is a species of seaweed native to Australia & New Zealand.
It is abundant on low-energy rocky reefs at mid-tide levels and easily outcompetes all other algal species due to its high tolerance to dehydration. Each pearl on Neptune’s Necklace has a slimy skin that conserves moisture inside it. The necklaces are made up of strings of olive-brown, spherical, gas-filled grapes, which taper toward a small anchor which is easily dislodged from the rock. These spheres rise to the surface of the water at hightide seeking sunlight and moving with the flow of the current.
Neptune's necklaces can reproduce asexually from broken strands. The form also reproduces sexually by means of sex organs that dot the surface of each bead. These are visible to the naked eye as rough-looking goosepimples