Refering back to the dunes post (Friday 7th Nov).
The Shipworm isn't a worm, it's a bivalve mollusc - like Mussels, Clams, Cockles etc. The valves have been modified to 'chew' through the wood and to prevent the hole collapsing and crushing the soft worm like body the animal lines the hole with a stiff calcareous tube.
Most of the large pieces of wood washed up on the beach have signs of infestation and they were a serious problem to mariners of old in wooden ships. Christopher Colombus had a copper sheath over the hull of his ships to keep them at bay.
Where to next? If time allows there might be some more gull pictures obtained.
In the meantime let us know what you have found in your outback.