Water inside swing arm?

[Jamieg285]

Had my tyres replaced on Friday.  As I watched the mechanic remove the rear wheel, a lot of water ran out of one side of the swing arm.  Difficult to tell how much, but from the size of the puddle and the time it took to stop draining, I'd say about a cup full.


Anyone seen this before?


This can only be rainwater, but should I be concerned about it?  Should I be trying to locate the inlet and plugging it, or maybe drilling a drain hole?