Oysters are considered halal by many Muslims, but others disagree.
The big rule in Islam is that everything is allowed unless specifically mentioned to be haram based on Quran and Hadith. Hadith is the traditions and sayings of the Prophet Mohammad. Saying of anyone else is not considered Hadith.
There were several rulings in Islam about land animals and how to tell Halal from Haram. But as for the ocean, there is one general ruling: it is all halal. Eat and enjoy.
What someone else mentioned about seafood that does not have scales is haram. That person is quoting the traditions and rulings of Shia. The Shia sect is a small sect representing less than %15 of the Muslim population, so their opinion is only valid for the followers of their ways.
Listen to the view on Oysters And Seafood by Shaykh Assim Al Hakeem
List of Halal and Haram Seafood
Shellfish, also known as aquatic shelled fish, are crustaceans. Some basic examples are prawns, oysters, shrimps, lobsters, and crabs. Many Islamic scholars have stated every type of shelled seafood as halaal. Therefore, crabs, lobsters, shrimps, oysters, and prawns can be considered eatables.
In the Sunni sect, three School of thought out of the total four declares the shellfish as eateries. The Hanbalis, Shafi’i, and Maliki said these all are healthy and halaal. Out of them, only Hanafi is against it, which states that they are Makrooh (detestable).
Frogs; Halaal or Haraam?
Many Islamic Scholars have stated frogs to be haram. It can be proved that our beloved Prophet (PBUH) has recommended His followers not to kill it. Thus, they aren’t edible for us and are also haraam, consequently.
حَدَّثَنَا مُحَمَّدُ بْنُ كَثِيرٍ، أَخْبَرَنَا سُفْيَانُ، عَنِ ابْنِ أَبِي ذِئْبٍ، عَنْ سَعِيدِ بْنِ خَالِدٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ عُثْمَانَ، أَنَّ طَبِيبًا، سَأَلَ النَّبِيَّ صلى الله عليه وسلم عَنْ ضِفْدَعٍ يَجْعَلُهَا فِي دَوَاءٍ فَنَهَاهُ النَّبِيُّ صلى الله عليه وسلم عَنْ قَتْلِهَا .
Narrated AbdurRahman ibn Uthman:
When a physician consulted the Prophet (ﷺ) about putting frogs in medicine, he forbade him to kill them.
There is a scientific fact as well behind being forbidden from eating them. With the vast development in biology, we know that frogs play an essential role in balancing the ecosystem.
As per a study followed by Physics.org, frogs are essential in maintaining the populations of insects in the bay area. They are a significant source of food for the birds and the fishes. Their extinction might leave enormous destruction over the entire food chart.
Alligators and crocodiles; Halaal or Haraam in Islam?
Many Islamic scholars have stated crocodiles and alligators as haraam. The reason is that these predators maintain fangs. They also live on both; land and water area.
Per the teachings of our Holy Qur’an, every animal that may cause harm is considered haraam in terms of eating them as meals even if they directly appear from the sea area. Eating such dangerous animals is forbidden, as constructed by the Holy Qur’an. It directs by saying:
4:29
يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ لَا تَأْكُلُوٓا۟ أَمْوَٰلَكُم بَيْنَكُم بِٱلْبَـٰطِلِ إِلَّآ أَن تَكُونَ تِجَـٰرَةً عَن تَرَاضٍۢ مِّنكُمْ ۚ وَلَا تَقْتُلُوٓا۟ أَنفُسَكُمْ ۚ إِنَّ ٱللَّهَ كَانَ بِكُمْ رَحِيمًۭا ٢٩
O believers! Do not devour one another’s wealth illegally, but rather trade by mutual consent. And do not kill ˹each other or˺ yourselves. Surely Allah is ever Merciful to you.
Are Octopus and Squids Haraam or Halaal in Islam?
Many Islamic scholars from Hanibal, Maliki, and Shafi’i have stated that squids and octopuses are halaal and edible seafood. Just the scholars from the Hanafi side have declared them as Makruh. Squids and octopuses are sea animals, and Allah has made a lot of sea creatures that aren’t haraam or harmful to eat. Just as fish is edible, octopuses and squids are eatable without slaughtering.