Session with Year 11 Enviro Science Students. Found 3 different Leatherjackets in the high tide line within a short distance of each other (unusual enough on its own). The largest had something protruding from it's anus. I pulled on it and out came a perfect specimen (albeit slightly covered in rotting leatherjacket juice) of a large and assumedly parasitic crustacean. This was much to the delight and disgust of everyone.