Crab belongs to marine life. They live entirely in water, or their habitat is in water, whether in fresh or salt water. Confusion arises because many assume that there is a kind of crab that is not halal as it can live in two realms, the sea and on land.

However, crabs can only survive in one of these realms and not both. With that, crabs are halal as long as they are not poisonous or harmful to humans.

Mazhab Shafi'i, Maliki and Hanbali opine that all kinds of marine animals are halal, including their carcasses. This is based on the word of Allah in surah Al-Maidah which reads:

"أحل لكم صيد البحر وطعامه"

Which means: "It is lawful for you to hunt down the sea and the food (from the sea) as a delicacy for you." (Al-Maidah: 96)

In a hadith narrated by seven companions:

"هو الطهور ماؤه الحل ميتته"

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

There are some sea creatures that can live on land for long periods of time such as penguins. These animals need to be slaughtered before they are eaten.

Al-Kharshi has said in his book ("Hasyiah Al-Kharshi Alaa" Muskhtasar Sayidi Khalil): "what is permissible to be eaten of sea creatures are all kinds of animals, whether they are already dead, are drowned or floating”.

Imam An-Nawawi has said: "The dead fish that are floating are halal. i.e, fish that died suddenly. So, it is permissible according to our opinion (Mazhab As-Shafi'i) for all kinds of sea animals except frogs..."