You are most likely thinking about a deduction for mariners that are assigned aboard ship. Such a deduction is not allowed.
http://gcaptain.com/maritime/blog/mariners-kappsized-by-the-irs/
While some mariner employers may pay per deim to their crew, you can not take a deduciton for meals you do not pay for. If you recieve a per deim and you pay for your meal, you can deduct the difference between what you paid out from what your employer paid you. (qualified per diem plan)
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