How did Impel Down's staff not know Buggy was a devil fruit user?

Question

How did the staff of Impel Down not know Buggy had a devil fruit when they put him in ?
Don't they dunk prisoners in boiling water?
Seriously how did Buggy get by these people ? Is Impel Down security that bad ?

Answer 1

There is a lot of questions there, and some led by some misundertandings.

How did the staff of Impel Down not know Buggy had a devil fruit when they put him in ? Seriously how did Buggy get by these people ? Is Impel Down security that bad ?

The reason why Buggy was able to overcome ID's security system remains unknown. Buggy is discovered by Luffy in Chapter 526 and it is just said he managed to hide his power, without further explanations. I don't know for the anime so if someone could check that would be awesome. I believe the scene takes place on episode 420~.
However, it is easy to make some assumptions :

The fact is, Buggy has only a 15 millions berries bounty on his head, which is pretty low. His very low bounty is also the reason why he was sent to the first level of Impel Down, because as he stated himself in chapter 549, every prisoner from level 2 that escaped with him has a higher bounty than him.

His insane luck must not be forgotten either as he shows an incredible ability for deceive others (e.g. Impel Down break led him to become the Shichibukai replacing Teach) without doing even doing it on purpose (even if he often looks stronger than he actually is, not weaker).