My favorite "ice cube trays" are reused 12 ounce Philadelphia Cream Cheese tubs. Water freezes solid in one of these tubs in less than eight hours and the "cubes" pop out with ease. I drop one or two of these cubes in my male animals' water buckets a few times each sizzling summer day and they always have cool, tasty water to drink (besides, it gives me an excuse to eat more bagels). 

I also use them to quick-cool the bottles of yummy raw goat milk I put in our refrigerator every day. After filtering the milk and pouring it into bottles, I fill our kitchen sink with cold water and unmold two Philly "cubes" in it. When the cubes have melted, the milk is chilled and ready to refrigerate or freeze.

Other plastic tubs work but (so far) none have held up like the Philly tubs do. I have some in my freezer that I've used every day for over six months. Now that's durable!

A good way to cool larger water sources such as horse tanks: freeze water in plastic soda bottles or milk jugs (allow enough head room for the freezing water to expand), then drop the bottles or jugs in the tank. When the ice has thawed, put the jugs or bottles back in the freezer overnight and they're ready to go again. These work exceptionally well in picnic coolers too.

Sue