The Scene: Flight deck of Springbok flight to the UK.
F/A comes to flight deck and asks crew what they'd like for dinner. Captain asks what's available. F/A replies "Chicken, beef, duck and fish." Captain asks "What's the duck like?" After a few moments hesitation the F/A replies "It's like a chicken but it swims."
Crew collapse in merriment and confused F/A hurries from flight deck.