white worm

Question
QUESTION: Having recently moved I cleaned out three ponds neglected for years.  In the smallest, about a square mete, I spotted a white worm, about 80 mm long, digging into the small amount of debris that I left in it.  What is it?  Is it useful or harmful?  I have failed to find anything on the internet except about small white worms - which clearly it isn't.

ANSWER: Hi Martin,

Thanx for your question.  What is your location, pond conditions and weather.  I know this sounds strange but I get inquiries from all over the planet.  
thx,
Tom

---------- FOLLOW-UP ----------

QUESTION: I'm in UK.  Since sending you the question I believe I have found the answer - it is probably a common earthworm that fell in while I was cleaning out - I can see the typical saddle on it.  It's likely that it looks white because it is perfectly clean and doesn't get much to eat to fill it's gut.  I have learned that such worms do not drown, but I'm still surprised that it's still active after 2 weeks or so.  When present bad weather clears I'll rescue it.  Thanks, Tom, for responding to me - and possibly I've given you a little more knowledge.

Answer
Martin,
Thanx for the info.  I notice a large influx of earthworms after a rainfall but the water will eventually kill them as they eventually drown.  I do know that there are differences between Old World and New World earthworms although I couldn't tell you if being able to survive for long periods of time in water is one of them.  My earthworms will eventually drown.  Thanx Martin.
Tom