Islam encourages Muslims to consume what is lawful and pure. According to the majority of scholars, seafood, including whales, crawfish, and other sea creatures are lawful to eat. When the Prophet (peace and blessings be upon him) was asked about the sea, he replied, “Its water is pure and its dead are halal.” (Ahmad)
It is also reported, on the authority of Jabir, that the Prophet (peace and blessings be upon him) once sent some of his Companions on an expedition. They found a dead whale by the sea and subsisted on it for more than twenty days. On their return to Madinah, they told the Prophet (peace and blessings be upon him) about this and he said, “Eat the food which Allah has brought forth for you and feed us from it if you have any left.” They then brought him some whale meat and he ate it (Al-Bukhari).
Dr. MuzammilSiddiqi, president of the Fiqh Council of North America, states the following: In the Qur’an, Allah Almighty says, [Lawful to you is (the pursuit of) water game and its use for food – for the benefit of yourselves and those who travel, but forbidden is (the pursuit of) land game as long as you are in a state of Ihram (for Hajj or ‘Umrah). And fear Allah to whom you shall be gathered back] (Al-Ma’idah 5:96).
Some jurists interpret the word “ta’amuhu” (meaning food that comes from the water) as being fish only. But other jurists take it to mean anything that lives in the water and is edible. The latter is the majority opinion and it is closer to the language of the Qur’an. I am inclined to take the majority opinion. Majority of the jurists consider shrimps, shark, whale, and all other types of seafood permissible to eat.