||[On the other hand], all creatures in seas and rivers that do not have fins and scales, whether they are small aquatic animals or other aquatic creatures, must be avoided by you.
Vechol asher eyn-lo snapir vekaskeset bayamim uvanechalim mikol sherets hamayim umikol nefesh hachayah asher bamayim shekets hem lachem.
||They will [always] be something to be shunned. You must avoid them by not eating their flesh.
Veshekets yiheyu lachem mibesaram lo tochelu ve'et-nivlatam teshaketsu.
|small aquatic animals|
(Rashi). Sheretz haMayim in Hebrew. Some say that this expression denotes animals that reproduce assexually (Ibn Ezra). It may possibly include all invertebrates.
|other aquatic creatures|
Larger creatures (Rashi), or those that reproduce sexually (Ibn Ezra). This includes aquatic mammals (Sifra).
Sheketz in Hebrew. Also denoting vermin, or something that is abhorrent, detested, shunned, repulsive, or loathesome.
Even when the laws of purity do not apply. (Cf. Ralbag; Leviticus 11:8).