“thrown in at the deep end” or “thrown in the deep end”

[opooo]

the following is original text, but I don’t know why there is a “at”

“On my first day at my new job I was thrown in at the deep end, because my boss was ill and I had to deal with all the problems by myself. ”

 

[Rover_KE]

Both versions are used. I detect no difference in meaning.

 

[emsr2d2]

The following is the original text no comma here but I don’t know why there is an “at”.

“On my first day at my new job I was thrown in at the deep end no comma here because my boss was ill and I had to deal with all the problems by myself.”

Note my corrections above. Start every sentence with a capital letter and end every sentence with an appropriate closing punctuation mark. What do you mean by "original text"? Did you copy it from somewhere else or did you write it yourself?