But anything in the seas or the rivers that does not have fins and scales, of the swarming creatures in the waters and of the living creatures that are in the waters, is detestable to you. You shall regard them as detestable; you shall not eat any of their flesh, and you shall detest their carcasses.
Leviticus 11:10-11
Don't eat shellfish, cetaceans, sharks, catfish, or cephalopods. God wants us to see them as detestable. He wants us to look at them and say "Eww! No way!"
There are a couple of words translated as "detestable" and "abominable" in the Old Testament. The word used to describe unclean animals that people shouldn't eat means exactly what it seems to mean in this verse: it's disgusting. That's God's opinion, not mine.
https://soilfromstone.blogspot.....com/2021/03/detesta
You shall not eat any of their flesh [of unclean animals], and you shall not touch their carcasses; they are unclean to you.
Leviticus 11:8
Rashi believed that this command only applies to the priests, but the plain meaning of the text says otherwise. On the other hand, I think that "don't touch their carcasses" is an emphatic repetition of "don't eat them". In other words, "Don't eat them and don't even think about eating them." It's not a prohibition against burying your pet dog. In any case, it's an easy command to keep. If you need to dispose of the body of an unclean animal, use gloves and a shovel.