Sunan an-Nasa'i, Volume 5, Book 42, Hadith 4355 (DarusSalam) ⓘ
It was narrated from Abu Hurairah, that the Prophet (said), concerning the water of the sea: "Its water is pure (and Purification) and its 'dead meat' is permissible (to eat)."
أَخْبَرَنَا إِسْحَاقُ بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ، قَالَ حَدَّثَنَا مَالِكٌ، عَنْ صَفْوَانَ بْنِ سُلَيْمٍ، عَنْ سَعِيدِ بْنِ سَلَمَةَ، عَنِ الْمُغِيرَةِ بْنِ أَبِي بُرْدَةَ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم فِي مَاءِ الْبَحْرِ " هُوَ الطَّهُورُ مَاؤُهُ الْحَلاَلُ مَيْتَتُهُ " .
also referenced under: Hadith 4350 (Reference) & Book 42, Hadith 88 (In-Book)