[[File:Zwierzęta wodne EN.png|400px|right|Water animals are kosher, if they have fins and scales.]]
Again, there are two conditions that must be met at the same time: a water animal ought to have both fins and scales to be kosher. This means that Jews can enjoy many popular fish species, such as herring, salmon, cod, tuna or pike. One should be careful with carp, as some varieties have no or very few scales. To be sure, Some rabbis have specified that a fish must have at least three scales, so count them when in doubtalthough most agree that one scale is enough as long as one is certain that the scale belongs to the fish and just stick to its skin after detaching from a fish of a different species.<ref>{{Cyt | nazwisko = Blech | imię = Zushe Yosef | tytuł = Kosher Food Production | url = https://cupdf.com/document/kosher-food-production-. html?page=139 | wydawca = Wiley-Blackwell | rok = 2008 | strony = 124 }}</ref> What's more, the scales must be visible with a naked eye and easily removable without tearing the skin, which makes such fish as eel, sturgeon and shark unkosher. And anything that lives in water, but is not a fish, that is, all kinds of non-fish seafood, isn't kosher either.
Now, have you ever heard of a traditional delicacy, still popular in Poland, known as "Jewish caviar"? Is Jewish caviar even possible? Anything that comes from an unclean animal – meat, milk, eggs, etc. – is unclean. So don't be fooled: if the sturgeon isn't kosher, then neither is sturgeon roe. Jewish "caviar" is nothing more than fried goose liver that has been chopped so finely it kind of resembles caviar – in the way it looks, at least, because it certainly doesn't taste the same.