Clogged drain

Before using Drain-o, Liquid Plumber, or a baking soda/vinegar/boiling water concoction, do a little dirty work. Take off the drain cover and use needlenose pliers, tweezers, and/or a crochet hook (the one you bought to teach yourself how to crochet, but haven't yet) to fish the junk out. Gag a little, take a shower to wash the jibblies off and watch the water drain nicely.
Nothing in a residential drain could compare to the horrors I witnessed while doing this. Those gobs of soapy hair still haunt my darker dreams.