The MTI Adventure Wear Under Dog ($39.99) literally turned the life jacket concept for dogs upside down. Instead of having flotation concentrated on the dog's back and sides, the flotation of the Under Dog is concentrated underneath the dog to provide a lifting action. There's also good flotation under the neck and chest to keep the head high, but most of the flotation is under the dog's belly.

The adjustment straps for this jacket goes around the dog's girth like all the others, but the final adjustments with buckles are made on the dog's back. This feature was a hit with many of the dog's owners because they didn't have to reach around and under their dog to fasten and tension the jacket.

Once the dogs entered the water we immediately observed the effect of having flotation under the dog, as opposed to having it on the back. By having the flotation under the dog, they tended to float much higher and more level. For small dogs, this was a concern for some of the owners because it appeared as though the dogs had to work hard to stay upright. One owner commented that she was afraid her dog would "capsize" and wouldn't be able to right himself. In general, this jacket scored lower for small dogs.

In contrast, this jacket clearly had benefits for larger dogs because it kept the rump considerably higher and more level. The flotation under the neck and chest was apparent too as it appeared as though the dogs didn't have to struggle as much to keep their head up. The dogs were also more visible in the water since they floated higher and the manufacturer's color choice of yellow and red made spotting even easier. Floating level had some additional benefits we hadn't considered. For example, instead of the dog's legs "bicycling", the dog's level attitude had them moving forward with a much more efficient stroke.

Unfortunately, this jacket earned some low marks for comfort on land. As you can imagine, with all the flotation under the dog, it was more difficult for the dog to sit or lounge around.