Two seaweeds, nowadays more properly known as macroalgae
The coralline (I'm not game to say which species) is brittle and has been bashed on its way to this between-tide resting place on the beach. But the Codium fragile is floppy and as fun as its common name, much more fun and inspiring than the more proper (imposed 'common'?) name, branched velvet weed. Yes, it is velvety, but that's like telling a child with new rubber boots that a puddle is a meeting of declivities in a road-surface. Velvet ignores the potential of the codium fragile (which isn't as fragile as all that), for as soon as a normal person picks up this seaweed as a freshly sea-disgorged clump (inevitably finding it as limp, bouncy, and boneless as a rubber chicken) the healthy impulse is first, to waggle it so that its fingers flop around – and then to throw the hand in some unsuspecting innocent's face.
Seriously now, recommended reading:
The Intertidal Rocky Shore by J Floor Anthoni, Seafriends
– Informative, passionate, and excellent pictures, too
Macroalgae: Prime Facts by Dr Alan Millar, Principal Research Scientist, Royal Botanical Gardens, Sydney, NSW Department of Primary Industries, June 2009
– Beautifully communicative –"With few exceptions, macroalgae are strictly benthic plants; that is they are always attached to the seabed or a solid substratum such as …" – and also a life-preserver to those of us willing but unable to identify –"The Australian continent hosts the richest marine macroalgal flora in the world with some 3000 species documented. The southern coast of Australia has about 1200 of these species."