The only animals that survive comfortably on both worlds, land and water, are those termed as amphibians. There are only three types of amphibians: frogs/toads, ceacillians, and salamanders. These animals, according to the Syafii Mazhab, are Haram.
Some may confuse crabs as animals that live on two habitats. however, this is a wrong assumption as crabs are considered as marine animals and all marine animals are Halal.
In relation to this, we quote the Hadith narrated by Abu Hurayra about a man who came to the Messenger of Allah, and said: Messenger of Allah! We travel by sea and we do not carry fres water with us so if we perform wudhu with it we go thirsty. Can we perform wudhu with sea water? The Messenger of Allah replied, its water is pure, and its dead creatures are halal.