Spiders are far too clever to 'fall' anywhere, including sinks and baths. They move around the house, and get stuck in baths because the sides are slippery, hence the OWT that they come up plug holes. As for this one, could you seriously imagine a spider allowing itself to wander into someone's wet mouth, with breath coming in and out? Hardly likely, or that you would not feel a spider tripping lightly across your face. Nah, it's another urban myth - file under "...and they told her she absolutely mustn't look back ...." and similar aprocryphal tales.