What is the ruling on the prayer of a marine engineer who travels frequently due to the nature of his work; does he pray the traveler's prayer or the normal prayer, and what should he do if the time for prayer comes during his shift and he cannot leave his work?

A man who travels a distance that permits shortening prayers (qasr) is treated as a traveler, even if he spends most of his time traveling.

If the time for prayer arrives and he cannot perform it during his work, then if he hopes to finish his work before the prayer time expires, he should delay the prayer until the end of its time to perform it in full.

However, if the work is continuous and cannot be left, then he must perform the prayer in the state he is able to, and it is not permissible for him to abandon it or delay it beyond its time.

If his shift begins after the time for Dhuhr or Maghrib prayers has entered, and he knows that he will not finish until after the time for Asr or Isha prayers has expired, then he may combine Dhuhr and Asr, and Maghrib and Isha, by performing them earlier (jama' taqdim).