Pretty straight forward...

In the film Cedric tells Harry he should take a bath with the egg to be able to learn the clue. It makes sense after the fact that mermaids only sing under water and etc., but is there any indication to how Cedric figured this out?

  • 3
    You are asking multiple questions here. Split it or it'll get closed.
    – user931
    Jan 1, 2018 at 23:30
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    Granted, there are two questions there, but I think they are easily linked... if it really bothers you however, go with the main question that brought you here...
    – Odin1806
    Jan 1, 2018 at 23:33
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    You are asking: 1. How did Cedric know? 2. Is warm water required? 3. Was egg modeled after mermaid's egg?
    – user931
    Jan 1, 2018 at 23:36
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    Mermaid's egg part made me laugh. You're talking like they are eggs of some real world animals. Harry Potter universe certainly never showed mermaid's eggs.
    – user931
    Jan 1, 2018 at 23:38
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    What I really want to know is how anyone would have deduced to place the egg under water. Is mermaid language, above and under water, common knowledge in the wizard world?
    – atw
    Feb 28, 2020 at 21:33

2 Answers 2


Moody tipped him off. Though it is actually

Barty Crouch Jr.


I knew you hadn’t worked out the egg’s clue, so I had to give you another hint —”
“You didn’t,” Harry said hoarsely. “Cedric gave me the clue —”
“Who told Cedric to open it underwater? I did. I trusted that he would pass the information on to you. Decent people are so easy to manipulate, Potter. I was sure Cedric would want to repay you for telling him about the dragons, and so he did.

Anyways the book doesn't say anything about it being warm water or not. But given that the eggs are supposedly supposed to about mermaids, and the hogwarts lake isn't the most cozy and warm place, then it should be so.

We don't know what mermaid eggs look like, so how would we know if the egg was based off of it?

  • This is an answer to the 1st question as per requested by the second comment
    – bleh
    Jan 1, 2018 at 23:40
  • As I mentioned in my question, I have only read some of the books, and that was a while ago. I was thinking that maybe something else mentioned how he may have known. Isn't the new 'magical beasts' thing in the same universe? Maybe there is a picture of a mermaid egg there...
    – Odin1806
    Jan 1, 2018 at 23:50

In the film too, after Harry returns from the graveyard with Cedric's dead body and "Moody" takes Harry away to his office, we see his Polyjuice potion start to wear off. He tries to take a swig of some more from his flask, but he has run out. As he is scouring his office for more, he slips up asking, "Were there others? In the graveyard, were there others?" When Harry hesitates and says, suspicious, "I - I don't think I said anything about a graveyard, Professor," Barty Crouch Jr gives his confession:

Barty Crouch Jr: "Marvellous creatures, Dragons, aren't they". Did you think that miserable oaf would've led you into the woods if I hadn't suggested it? Do you think Cedric Diggory would've told you to open the egg under water if I hadn't told him first myself? D'you think Neville Longbottom, the witless wonder, could've provided you with Gillyweed if I hadn't given him the book that led him straight to it? Huh?

This is where Harry then works out "It was you from the beginning".

  • 2
    It seems your saying exactly what the accepted answer that was posted 5 hours earlier is saying. Could you elaborate on anything new you may be trying to add?
    – Gnemlock
    Jan 2, 2018 at 6:40
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    I disagree. @Au101 gave the quote from the movie and not the book. So the people who haven't read the books and just seen the movies will be able to relate.
    – dobby
    Jan 2, 2018 at 6:44
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    @Gnemlock pretty much what Dobby said. I read the OP and I noticed "In the film Cedric tells Harry he should take a bath with the egg to be able to learn the clue. It makes sense after the fact that mermaids only sing under water and etc., but is there any indication to how Cedric figured this out." In my mind the films and the books might as well be separate works, especially GoF, all the nuts and bolts of GoF are different in the movie, for example Barty Crouch Jr being present in Harry's dream at the start. I thought it might interest the OP to know that the explanation was in the film
    – Au101
    Jan 2, 2018 at 14:11
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    And help them with where to look out for it. I also wanted to give the films their due, this isn't an unexplained plot point even in the movies (unlike almost all plot points in the movies :P :P ) A lot of times the answer to a film question (even Star Wars, where the books are companion works) is: this isn't addressed in the movies, but if we go to the books ... But here it is addressed in the movies, so, I thought it was worth a mention
    – Au101
    Jan 2, 2018 at 14:12

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