Thus, for example, the local dish Laksa (which includes meats such as shrimp and squid with a soup base made from shrimp paste), is deemed permissible in the Shafi'i Sunni Muslim majority nations of Indonesia and Malaysia where it is commonly consumed.
Any other sea (or water) creatures which are not fish, therefore, are also makruh tahrimi (forbidden but not as the same level as haram) whether they breathe oxygen from water through gills (such as prawns, lobsters and crabs, which are crustaceans), molluscs such as clams, octopus, mussels and squid, especially if they breathe oxygen from air through lungs (such as sea turtles and sea snakes which are reptiles, dolphins and whales which are mammals, or semi-aquatic animals like penguins which are birds, saltwater crocodiles which are reptiles, seals which are mammals, and frogs which are amphibians).
Also the hanafi scholars prohibit fish which died of natural causes and starts to float on the surface of the water (also known as Samak-al-Tafi).
The requirement for gills is not part of any religious rule, but biologically it is an identifying characteristic of true fish.
According to the chok or divine decrees of the Torah and the Talmud, for a fish to be declared kosher, it must have scales and fins.
[8] Thus, a grass carp, mirror carp, and salmon are kosher, whereas a shark, whose "scales" are microscopic dermal denticles, a sturgeon, whose scutes cannot be easily removed without cutting them out of the body, and a swordfish, which loses all of its scales as an adult, are all not kosher.