Neptune's Necklace or Sea Grapes.

Description:

Hormosira banksii (known as Neptune's necklace, Neptune's pearls, sea grapes or bubbleweed) is a species of seaweed (brown algae, Fucales) found in Australia and New Zealand.

Habitat:

Seen washed up on the beack on a rocky shoreline along the southern coast of Australia.

Notes:

Commonly found in rock pools at mid-tide levels and is characterised by strings of olive-brown hollow beads. The beads have a slimy layer which conserves moisture. They also contain gas, allowing them to rise to the surface of the water