Is paying money to the guards of a prohibited marine sand exploitation site for construction purposes considered a bribe, or is it a legitimate way to obtain a job opportunity?

Paying money to sand guards to benefit from it is considered a bribe. If the state has prohibited benefiting from sand for a public interest, then bribery is forbidden for both the giver and the receiver. However, if the prohibition is not for a public interest, then it is permissible to pay the bribe if it is the only way to benefit from the sand, because sand is permissible (mubah (definition)) and no one has the right to prevent benefiting from it except for a public interest. In this case, the sin falls upon the receiver, not the giver.