It's likely you meant to ask: "Why did the salt water freeze *but* did [something else]?"
To answer your question, I need to know what the "something else" is. For example:
* "Why did the salt water freeze but did not freeze as quickly as fresh water?"
* This is because salt water has a lower freezing point than freshwater. The salt ions disrupt the formation of ice crystals.
* "Why did the salt water freeze but did not turn into a solid block?"
* This could be because the salt water was in a container that allowed some expansion during freezing. Saltwater expands as it freezes, unlike freshwater.
* "Why did the salt water freeze but did not kill the fish?"
* Fish can survive in saltwater that freezes over because the ice forms on the surface, creating a layer of insulation.
Let me know the rest of the question, and I can give you a more specific answer!
