Does a worker at sea pray qasr or itmam prayer?

If the ship is your brother's home and place of residence, then he prays his prayers in full and fasts, according to some scholars, even if he has no other home. Others are of the view that he takes the ruling of a traveler regarding shortening prayers and breaking the fast, due to the general texts that grant this to the traveler. However, if his travel on it is for work and he returns to his home, he may shorten prayers as long as he is traveling, and he must pray in full and fast if he intends to reside at his destination for more than four days.