A question about swear

If you don't mind, please give me a answer

English teacher who is teaching english in Korea inform me a swear.

But there is a spelling error, I think. So I come to this site and I need your help.

Let me know which sentence is correct,

"I'll beat the living crab out of you."

"I'll beat the living crap out of you."

He said the 1st. But I found that there is something wrong.

I can't find the example sentences using crab in the google.(frankly, it is funny lol.. what on earth living crab in my body is...)

so I confirmed the 2nd is right, for I can find many examples.

But he doesn't agree.......

What do you think about it???