“Olde mossie-backed divers” such as myself, were usually told the urine tale in our scuba classes in the late 1960s or early 1970s; but once we started to think about it, particularly as scientists (junior grade), it made no sense, whatsoever.
The moral is…never underestimate the power of nematocysts.
So you’ve been stung by a bristleworm. Your hand is burning and hundreds of tiny white spines are sticking out of it. What do you do?