He recalled: "Tom got stung by a jellyfish and he shouted across the beach, 'I say old sport could you come and pee on me?' and I engagingly obliged.
"I've since read up on it and it don't think it works - it's an old wives' tale."
The incident possibly stirred up unfortunate memories for the Golden Globe winner, who revealed his fitting nick name.
Hiddleston said that he had been picked on during his time in Eton, where he was ironically dubbed Piddleston.
Despite the £32,000-per-year school having a prestigious reputation, having educated the likes of David Cameron, Damian Lewis, Prince William and Prince Harry, Hiddleston revealed that he was picked on just like many schoolchildren.
"Very soon after I arrived I got the nickname 'Piddle'," he recalled, "and the boys made up the rhyme, 'Hiddle Piddle did a widdle in the middle of the night'.
"My closest friends still call me 'Pid' but it's affectionate now."
Hiddleston also revealed that he co-starred in a play alongside Oscar winner Eddie Redmayne while they were both at school, though with very different results.
"I was in A Passage to India with Eddie Redmayne, who played the female lead. I on the other hand, played the front leg of the elephant he rode," Hiddleston laughed.
The actor, best known for his role as Loki in the Thor franchise, is about to star in King Kong reboot Skull Island, out in New Zealand cinemas on March 9.