Det accepterade svaret är utmärkt, men jag vill tillägga att vi bara inte vet.
Inom verken är det inte ens 100% klart att Watcharen är en varelse eller ett antal oberoende ormar som varelser som arbetar tillsammans.
‘I felt that something horrible was near from the moment that my foot first touched the water,’ said Frodo. ‘What was the thing, or were there many of them?’ ‘I do not know,’ answered Gandalf; ‘but the arms were all guided by one purpose. Something has crept, or has been driven out of dark waters under the mountains. There are older and fouler things than Orcs in the deep places of the world.’ He did not speak aloud his thought that whatever it was that dwelt in the lake, it had seized on Frodo first among all the Company.
Även om det är extremt troligt att det var en varelse, och Kraken-teorin passar, kan vi inte säga säkert utan en viss spekulation.