gas under pressure takes the path of least resistence to escape. so even a pin hole is less resistence than the inch of water in the airlock.
if you have krausen, you're either in active fermentation, or damn close. don't worry about airlock bubbles too terribly much. they are handy, but flawed. a completely fermented beer can still make the airlock bubble. an unfinished beer may not bubble the airlock.
but looking at the beer, and testign after a week with a hydrometer...those are reliable means of knowing what's happening.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10