Leviticus 11:10-12

10But all creatures in the seas or streams that do not have fins and scales—whether among all the swarming things or among all the other living creatures in the water—you are to regard as unclean. 11And since you are to regard them as unclean, you must not eat their meat; you must regard their carcasses as unclean. 12Anything living in the water that does not have fins and scales is to be regarded as unclean by you.