Sayyiduna Jabir (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) was asked about the sea, and he (peace and blessings be upon him) said: "Its water is pure and its dead are lawful."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيد والذبائح / 18966