Sarcastic Fringehead
Neoclinus blanchardi

Sarcastics live in various kinds of shelters, such as
empty shells, bottles, abandoned burrows, or
cracks in clay or rock outcroppings.  Like this one,
they generally spend their time in their home,
with their head exposed -- waiting for a meal to swim by.

Sarcastics are very aggressive
and will attack just about anything.
You can easily coax them out of their holes
by waving a finger in front of them.
Just be prepared for them to lunge out and clamp on!