Life form and Sunset

We went for a stroll along Bastion Point this afternoon and found another example of the life form previously identified as a shark/ray egg case.  A reaction on Facebook to these images has suggested Sea Slug (a shell-less gastropod) and that seems to be a fruitful area for exploration!  We tried to get some definitive photographs of it but it didn't hang around.

Frances has used the sea slug hint to pull out her book on the wildlife of Coffin Bay (about 1400 kms NW of Mallacoota) "Shores and Shallows of Coffin Bay" and found a very close match with Sydney Sea Hare Aplysia dactylomela.

It seemed to swim off with purpose to get away from us.  I can appreciate that egg cases have flaps but this seemed to have clear self motivation to swim off. using the flaps like fins

I am beginning to wonder it it is a hatched egg case.  However as it took off it squirted this purple liquid out the back - reminding us of coelenterate defensive techniques.  Do sharks or rays do this as well?

In attempting to ID this life form as a sea slug I feel as though I have entered a parallel universe!

1. It appears there are 400 species of sea slugs in Port Philip; 
2. There used to be an Australian Sea Slug Forum run by the Australian Museum with 23,000 posts until it closed due to lack of funding;
3. There is a Facebook group for the Sea Slug Census (an interesting adaptation of an application designed to identify hot chicks for randy frat-boys).

I am joining the third of these, so watch this space.

Back home the sunset was well up to standard.