We sampled Puget Sound water and ocean water. Well, not straight from the source but tasted the amount of salitity there would be in each. We also learned that we would die if we only drank saltwater. This is because the salt dehydrates you. Good thing we had fresh water to quench our thirst afterwards.
We then took part in an experiment that demonstrated the weights and properties of water that is cold, warm, frozen, fresh and salty. As your child what he/she learned!