Ocean water contains high levels of sodium, which can lead to dehydration and other health problems in dogs.
Pool water contains chemicals that can irritate your dog's skin and eyes, and can also cause nausea and vomiting if swallowed.
Lake water can contain bacteria and parasites that can make your dog sick.
River water can also contain bacteria and parasites, as well as pollutants that can be harmful to your dog.
Puddle water can contain all sorts of things, including bacteria, parasites, and even antifreeze.
Toilet water contains bacteria and other harmful substances, and can also make your dog sick if ingested.
Hot tub water can be too hot for your dog, and the chemicals in it can also be irritating.