Sayyiduna Anas bin Malik (may Allah be pleased with him) narrated the account of Sayyiduna Abu Talhah (may Allah be pleased with him), and in it he said: He set out on the sea and died, and his companions found no island on which to bury him until after seven days; so they buried him there, and he had not changed.
Hasan al-Basri (may Allah have mercy on him) says: He is to be washed, shrouded and prayed over, and then cast into the sea. In another narration: "He is placed in a basket and then cast into the sea."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6774