Originally Posted by michaelfung
Fish is good for your health. - food - uncountable noun
People eat lots of different types of fish. - There are different types of fish that people eat. There is more than one type. It's possible to count them.
Fish are cold-blooded. - living creatures - countable
fish - singular and plural
It's possible to use "fishes" as the plural form. However, I usually use "fish" for the plural form, and I would say most others do as well.