We did an experiment about freezing water and comparing fresh water and salt water.
First we used two glass jars. One with regular water, and the other with water and 2 tablespoons of salt mixed in.
Now put them in the frige and record what you see every 10 minutes for an hour.
After 30 minutes there was a nice thin layer of ice on the top of the fresh water and nothing yet in the salt water.
Then in 40 minutes, there was a little thicker layer of ice all around the edges and top of the fresh water and still nothing noticeable in the salt water.
After completely frozen for the rest of the day. The fresh water was hard as a rock. The salt water was frozen, but frosty in look and more slushy in appearance.
Seeing the difference in the clarity after it started thawing a little bit.
See for yourself!