Your hovercraft is full of eels? This phrase has been a riddle or an idiomatic expression for a long time now. It is said to have originated in the 1960s and was popularized by Monty Python's Flying Circus, a British comedy show. The origins of the phrase are not entirely clear, but it appears in several sketches and is often used to illustrate confusion or misunderstanding between people.

So, if someone says "My hovercraft is full of eels," they are probably trying to convey that they don't understand what you're saying or that the situation is not as expected. It can also be a humorous way of expressing confusion or disbelief in any context.