Shit across the bows

On realising that last night’s disturbingly authentically Greek kebab mixed with large amounts of disturbingly authentic Greek wine will be unlikely to make it through the hand operated flush system aboard The Good Ship Aqualung, you are required to launch yourself into the Mediterranean, swim forward to the anchor chain and cling to it while voiding your bowels. All crew will pretend this is not happening but tell you about the number of fish feeding on your turds.

Also known as Laying Deep Sea Cable or Having a Matthew White (rhyming slang)