Is it permissible to eat crabs as they are not only sea creatures but also survive on land?

There is no doubt as to the permissibility of eating the meat of such creatures. God says in the Quran: "Say: 'In all that has been revealed to me, I do not find anything forbidden to eat, if one wishes to eat thereof, unless it be carrion, or blood poured forth, or the flesh of swine - for all that is unclean - or a sinful offering over which any name other than God's has been invoked" [6: 145].
Referring to the sea, the Prophet (peace and blessings be upon him) said: "Its water is pure and purifying and its dead creatures are permissible to eat." Guided by these and other texts, we maintain that crabs and similar creatures, like fish and sea mammals, are all permissible to eat even if they die of natural causes or merely by being taken out of the water.
And God the Almighty knows best.