How should the marine pilot pray and shorten his prayer, and how does he determine the Qibla as the direction of the vessel changes?

It is sunnah for a traveler, whether by sea or land, to shorten the four-rak'ah prayers and combine prayers when needed. Determining the qiblah is possible with modern instruments. The traveler must pray facing the qiblah for obligatory prayers and should turn with the ship. As for supererogatory prayers, one faces the qiblah at the beginning, and then a change in direction does not matter. If it is impossible to know the qiblah and there is a fear that the time for the obligatory prayer will expire, one should exert their best effort and pray. Re-performing the prayer is not incumbent upon them if they later discover they were mistaken.