Warning: preg_replace(): The /e modifier is deprecated, use preg_replace_callback instead in ..../includes/class_bbcode.php on line 2958 A Guy's (& his girls') WORST NIGHTMARE!
Ok, when I first heard of this, my reaction was this has to be an urban legend.
Judge for yourself.
Candiru (Vandellia cirrhosa) are parasitic catfishes that feed on blood from the gill cavities of larger fishes. They are known to enter the urethra of humans urinating in water, possibly mistaking exiting urine for gill exhaust
Below are photos of a candiru and a photo of one being surgically removed by A. Samad from a male's urethra.