Mazhab as-Shafi'i, Maliki and Hanbali are of the views that all kinds of seafood are halal, including if it’s dead.

Imam Nawawi has said: "The dead fish that are floating are considered halal i.e. fish that died by itself. So it is permissible according to our opinion (Mazhab Shafi'i) for all kinds of sea animals except frog ... "

This is based on a hadith narrated by Abu Daud, At-Tirmizi, An-Nasa'i, Ibn Majah, Ahmad, Malik and Darimi which says:

"هو الطهور ماؤه الحل ميتته"

Which means: "The (sea) water is pure and its dead meat is halal."

Some of the scholars of the Hanafi School considered that when seafood is concerned, only the fish are Halal.