[Mdu]

Mdu asked the Naked Scientists:

If you fart in the bath under water why does it smell?

What do you think?

[Madidus_Scientia]

Maybe where the bubble comes up is closer to your nose than it would otherwise be.

[paul.fr]

Heat and concentration. If you are in the bath then the heat / steam will open your sinuses, not only that but heat will make the smell stronger. Your farts will also be in bubbles that pop between your legs and under your nose, if you are sat up, and you are in a confined space.

[blakestyger]

And perhaps there's a scrubbing effect so the less noxious soluble components are removed and the remainder is concentrated.

[lyner]

It all gets out in one bubble instead of having to diffuse slowly through two layers of clothing.
The humidity argument implies that it would be just as bad in a shower -and that could involve a more enclosed space for the gases to spread into. Is there a consensus on the relative smellyness out of doors, in a room, in the bath or in the shower?
Have you ever noticed how they seem to 'cling to you' even in a high wind, too? Some interesting aerodynamics at work there.