Not everything that comes from the ocean is halal unlike what some other sects might claim.
In our jurisprudence for example, one cannot eat fish that doesn’t have scales. Jurists also differ as to the amount of scales which must be present on the fish. For example, some fuqaha say that it is only allowed to eat a fish if MOST of the body has scales, and others say that even a tiny amount of scales is sufficient. It should be noted that prawns are also halal.
The above ruling are based on the ahadith such as the following:
Imam Al-Baqir (peace be upon him) said:
“Eat any fish that has scales, and do not eat what does not have scales."
[Al-Kulayni, Al-Kafi, Vol.6, p. 219]
May Allah grant you success