A man asked the Messenger of Allah ﷺ: Messenger of Allah, we travel on the sea and take a small quantity of water with us. If we use this for ablution, we would suffer from thirst. Can we perform ablution with sea water? The Messenger ﷺ replied: Its water is pure and what dies in it is lawful food.  

أَخْبَرَهُ أَنَّهُ سَمِعَ أَبَا هُرَيْرَةَ يَقُولُ سَأَلَ رَجُلٌ النَّبِيَّ ﷺ فَقَالَ يَا رَسُولَ اللَّهِ إِنَّا نَرْكَبُ الْبَحْرَ وَنَحْمِلُ مَعَنَا الْقَلِيلَ مِنَ الْمَاءِ فَإِنْ تَوَضَّأْنَا بِهِ عَطِشْنَا أَفَنَتَوَضَّأُ بِمَاءِ الْبَحْرِ فَقَالَ رَسُولُ اللَّهِ ﷺ هُوَ الطَّهُورُ مَاؤُهُ الْحِلُّ مَيْتَتُهُ