Sheikh `Abd Allah b. Fahd al-Hayd.
If there were such a thing as a sea turtle that could only live in the water and could not survive on land, then it would be permissible to eat it without slaughtering it, just as we may eat fish without slaughtering them.
However, though sea turtles live almost all of their lives in the water, they are fully capable of coming onto the land to lay their eggs and for other reasons. Because of this unique situation, they are a matter of disagreement among scholars.
Many scholars have ruled that they must be slaughtered like any land animal. Ahmad b. Hanbal said: “I see no objection to eating the meat of turtles provided they are properly slaughtered.”
And Allah knows best.
Source: Islamic Today