Seafood is an uncountable noun. Because Seafood means all seafood, it can't be counted by number, so it can't be counted. Example: Seafood unsettles my stomach. I feel sick when I eat seafood.

Bilingual examples 1, Try the seafood plate.

Please try this seafood.

2、Seafood is a speciality on the island.

Seafood is a specialty of the island.

3、The fish or seafood is heavily salted with pure sodium chloride.

Fish or seafood is salted with thick pure salt.

4、Seafood soup is a good appetizer.

Seafood soup is a good appetizer.

5、The common prescription is to primarily shop the grocery store, since that's where fresh produce, meat and seafood, and dairy are.

The usual method is to buy mainly in the grocery store, because there are fresh agricultural products, meat and seafood and dairy products.