"Its water is pure (and Purification) and its 'dead meat' is permissible (to eat)." (Using translation from Nasāʾī 4350)  

عَنِ النَّبِيِّ ﷺ «فِي مَاءِ الْبَحْرِ هُوَ الطَّهُورُ مَاؤُهُ الْحِلُّ مَيْتَتُهُ»