What are the rulings for prayer (combining and shortening) and fasting for Muslims working on ships whose voyages exceed 80 km, or are less than that with limited water, and in cases where the ship is close to land but water is only available three times a day?

The legitimate travel distance that permits shortening prayers (qasr) is equivalent to 83 kilometers. This ruling applies to all modes of travel: land, sea, and air. If a ship does not reach this distance, its passengers are not granted the concession for travel. However, if the distance is reached, their ruling is that of travelers, even if the ship stops for 24 hours. If it is possible to use seawater for ablution (wudu'), it is pure and must be used. If water or pure earth (tayammum) is unattainable for prayer, they should pray in their current state, and they are not required to make up the prayers later.