Any clue about such sword?
There's apparently a Hindu sacred text that contains an account of a sword being used to behead an elephant
Then, O great king, having uttered a loud shout, Bhima, sword in hand impetuously jumping on (Bhanumat's) excellent elephant aided by the latter's tusks, gained, O sire, the back of that prince of tuskers, and with his huge sword cut Bhanumat, dividing him in the middle. That chastiser of foes, then, having (thus) slain in battle the prince of the Kalingas, next 1 made his sword which was capable of bearing a great strain, to descend upon the neck of that elephant. His head cut off, that prince of elephants fell down with a loud roar, like a crested mountain (whose base is) eaten away by the impetuous (surges of the) sea.
So perhaps the book referenced this text?
Any reference about the technology of sword making with water soaked iron ore?
Perhaps a confusion regarding the "water marks" found on the surface of some high-quality Damascene swords made from Wootz steel.
Soaking ingots in water for years has no role in the process but might perhaps be a garbled account or folkloric fabricated "explanation" for the pattern.
The methods of producing this type of sword have been lost but one study suggests that the presence of certain impurities, unknown to the sword-maker, may have been essential.