I am up to my waist in water. (I am standing in a pool of water. The water reaches as high as my waist.)
He is up to his neck in water. (The water reaches up to (as high as) his neck.)
The boss is up to his neck in problems. (metaphoric, as if there were a pool of problems he was immersed in -- he is overwhelmed by problems)
The boss's chief of security is up to his neck in
industrial espionage. (metaphoric, as if he is being
overwhelmed by industrial espionage or as if he is involved in
industrial espionage -- perhaps he is being accused of espionage --
it's impossible to say exactly from this sentence alone.)
Your boss's chief of security is up to his Bahamian bank accounts in
industrial espionage. (doubly metaphoric, probably suggesting
that the person responsible for security is overwhelmed by or implicated in problems related to
industrial espionage. It's unclear without more context whether
the problems involve the Bahamian bank accounts or whether he himself
has such accounts or whether the accounts are related in some way to
his own activities or to accusations against him.)
I hope the explanation of up to ... in ...
was what you wanted, because without more information I can't guess
anything more specific about the bank accounts and the espionage.
CJ