This may drift into TMI territory:
I came across a number of people on another board who have seemingly noticed this phenomenon. Whilst sitting in the bath, any wind that is passed is seemingly a lot smellier than normal.
Obviously, this could be a fluke, as it’s impossible to examine the stench generated without it passing through water, but has anybody else noticed this?
Is there a reason why this should be the case?
Bath bong!
Sorry, just thought it sounded funny.
Maybe because it doesn’t get mixed with air immediately, and has gathered momentum toward your nose as it bubbles up from the water?
[anecdote]
Once I was standing in water up to my upper lip. I farted into my bathing suit, but the nylon trapped it inside. I mashed it out but it went between my legs and bubbled up the front, directly into my nose.
I almost drowned.
[/anecdote]
Same stink, the difference being that when you’re in the tub the release is captured in a few noxious fart bubbles rather than being dissipated through clothing and air. It’s in a more tidy package when the bubble pops and the subsequent bouquet rises through the stillness of the bathroom air.
I’d like to believe that the water removes all of the impuritites, leaving only the quintessential fart for you to ponder in the tub.
But that’s probably not the case.
Wouldn’t removing the impurities make it smell better? 
Well, normally yes. But with the nature of farts being what they are, we’re really on an inverse scale here. Very bizarro-ish.
WE’RE THROUGH THE LOOKING GLASS, PEOPLE!
Well, the air in the bath (it’s also pretty bad in the shower) is warm and humid. You smell things better when they’re in warm and humid air, don’t you?
My bathtub farts smell exactly the same as my farts that are aged to perfection and distilled in beechwood casks, so you may be on to something.
Now we need someone to experiment with passing farts through activated charcoal…
I think mack might have touched on it. Wouldn’t the pressure of the water condense the fart into a denser state?
Stuff some in your bum and get back to us. 
ooh ooh, I got a link too!
You folks need to work more cumin into your diets. 
Seriously, it really does decrease the F factor.