That's a famous quote from the movie "The Hitchhiker's Guide to the Galaxy" by Douglas Adams. The scene in which it appears takes place on an alien planet where two beings, Zaphod Beeblebrox and Trillian, are being transported across a lake using a hovercraft that is filled with eels.

In the quote, Zaphod says this line while observing his surroundings as they pass over the water. It's meant to be humorous because it doesn't make much sense in any practical or logical way - a hovercraft isn't typically associated with carrying eels, and "eels" are slippery fish that wouldn't hold up on such a vehicle.

The quote has become widely recognized by fans of the book series and movie adaptations. It's often used as an example of illogical or nonsensical dialogue in media where characters say things for comedic effect rather than because it makes sense within their world.