It was narrated that Ibn Firasi said:"I was fishing and I had a vessel with me in which I kept water, and I used seawater for ablution. I mentioned that to the Messenger of Allah and he said: 'Its water is a means of purification, and its dead meat is permissible.'"
حَدَّثَنَا سَهْلُ بْنُ أَبِي سَهْلٍ، حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنِي اللَّيْثُ بْنُ سَعْدٍ، عَنْ جَعْفَرِ بْنِ رَبِيعَةَ، عَنْ بَكْرِ بْنِ سَوَادَةَ، عَنْ مُسْلِمِ بْنِ مَخْشِيٍّ، عَنِ ابْنِ الْفِرَاسِيِّ، قَالَ كُنْتُ أَصِيدُ وَكَانَتْ لِي قِرْبَةٌ أَجْعَلُ فِيهَا مَاءً وَإِنِّي تَوَضَّأْتُ بِمَاءِ الْبَحْرِ فَذَكَرْتُ ذَلِكَ لِرَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ فَقَالَ " هُوَ الطَّهُورُ مَاؤُهُ الْحِلُّ مَيْتَتُهُ " .
IbnMaja
The Book of Purification and its Sunnah • Hadith 387