What is Crocodile's secret?


In chapter 540 we can see Ivankov mention Crocodile's weakness. What secret
weakness was he referring to?

![enter image description here](https://i.stack.imgur.com/OXYnv.jpg)




It was never stated so any response would only be speculation. With that said,
I don't think its the water weakness as Luffy already knows that and wouldn't
prompt the reaction Crocodile had. Most likely knowing Oda its something
embarrassing/silly.

