Why Does a Marble Fall Faster in a Pool Than in a Narrow Tube?

[ultraviolent]

Can anyone give me an explanation of why a marble dropped into a swimming pool will fall faster than if you drop a marble into a water filled tube with a diameter only slightly larger than the marble itself (presume it doesn't touch the walls of the tube). It's something to do with how quickly water can be displaced, but I can't come up with a good explanation.

Thanks,

 

[Danger]

You're pretty much there. Try thinking of a similar but different scenario. What would be the effect of setting off a firecracker beside a ping-pong ball as opposed to putting them both into a narrow tube and lighting it? Why?

 

[ultraviolent]

Thanks, I understand now :)