In reply to Godwin:
> the idea of a leech ...
Reminds me of a true story about an Australian reality show, one of those jungle "get me out of here" ones.
Anyway the competitors were equipped with radios and told they had medical support etc if they needed it, and sent off on their quest into the jungle.
Some time later, one of the hapless victims gets on the radio in a right state demanding the medic, who is duly found and enquires what seems to be the trouble.
"Ah well," says the victim, "I was swimming across this creek and I felt something going on in my trousers, so when I got to the other side I had a look and I saw the tail of a leech disappearing up my thomas. HELP - what do I do???"
At this point you need to imagine a proper Aussie accent.
"Well, mate, relax - there's absolutely nothing to worry about".
Pause.
"Just drink lots of water and the little critter'll pop right out again when you take a piss."