The basic ruling is that sea creatures which usually live in the sea are lawful, as Allah (Glorified and Exalted be He) says:
Lawful to you is (the pursuit of) water-game and its use for food - for the benefit of yourselves and those who travel
The Prophet (peace be upon him) said about the sea,
"Its water is pure, and its dead creatures are lawful (to eat)."
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.