Pez vs. Pescado
I was doing an exercise and noticed that it insisted "los pescados nadan."
I had a Spanish teacher who said that "pez" means the type of fish you would find swimming around while "pescado" is used exclusively for cooked fish.
Can anyone confirm?
If you want to be nitpicking, "pez" is while it's in the sea, while "pescado" is after it has been "fished". So, you say "pescado frito" (fried fish) but not "pez frito", and you say you have a "pez dorado" (gold fish), not a "pescado dorado". However, less educated people don't care about the distinction.