Salt water snail clings to a wet rock. Fitzroy Island, Qld.
Snail in a Half Shell
A snail, or a half snail, or a slug-snail. Victoria Point, Qld.
Sea snails remind me of weird little elephants. This one explores a mangrove leaf. Rules Beach, QLD.
Snail Parasite Fly
This large fly feeds on nectar and parasitises snails. Walkers Point, QLD.
Snail, I think you are missing some shell. Apparently some slugs have shell remnants partially or completely embedded beneath the skin. These are known as slugs because slugs are basically snails without a shell (they can hide in).