I have never taken my dogs out on water, but if I did, they would be wearing life jackets. Even dogs who are great swimmers can easily drown from fatigue. Just like people should be in life jackets, so should our dogs.
Kudos to you for realizing this!!!
I haven't used life jackets but do like the products that cleanrun.com offers. Clean Run is a dog agility website, but I see in their store that they have a life jacket offered. Clean Run is usually very picky about which products they sell, so I'd give it a good look. :)