Sunan Ibn Majah
388
Hasan Sahih+3

It was narrated from Jabir that:The Prophet was asked about seawater, and he said: "Its water is a means of purification, and its dead meat is permissible." (Hasan) Another chain with similar wording

Hasan SahihAl-Albani
Hasan SahihMuhammad Fouad Abd al-Baqi