I don't know if this is true, but I've read that in general, back then sailors would drink effectively alcohol either through beer or wine to quench their thirst, and water was mostly rationed since they'd have to stock up before the journey and after they make port somewhere. With only those highest in command having the privilege of drinking water while the sailors drank the wine.
Now if this were true, how did Islamic sailors deal with no or limited water on board when they were voyaging at sea? Alcohol is strictly prohibited so has there been any documentation in the last 1000+ years that details what they did during those days?
In fact, we have a fair amount of evidence of wine-drinking from the medieval Islamic world--both scholars' opinions and local practices regarding alcohol consumption were still in the process of bumping up against each other with no central authority to dictate a rule magisterially. But this is almost beside the point here: water. Sailors drank water. On rowed ships in the Mediterranean, up to four liters a day of it.
In fact, even when ship technology and navigation might have allowed crews to sail across the Mediterranean, in open sea, we know they preferred to coastline-hop in short spurts. An important reason for this was indeed the ability to refresh supplies frequently.
Even when wine was an option, as it was on ships crewed by both Christians and Muslims in the Aragonese fleet, we have some evidence that crews might have preferred to stick with water. There was a sharp rule in Balkans ports like Dubrovnik that only wine designated for sale in sealed containers could be sold on shore. That is, the wine for sailors' consumption that was leftover had to be dumped into the sea.
Yeah, as you can imagine, there was a very healthy black market for sailors selling excess wine in Dubrovnik. :D