prawn necklace
A twist on the pearl necklace. It's when a woman squirts all over a man's neck, after having been eaten out while sitting on his face... hence the smell of prawn, and the term "prawn necklace".
"Yo, Ethan, you going to call back that chick from the bar last night? Mercedes, was it?", "Nah, I took her home and she gave me a rancid prawn necklace."