Underdog by MTI

Like humans, some dogs are better swimmers than others. And like all swimmers, they will eventually tire. Even a good swimmer might be disoriented from the shock of falling in the water. Most pet life jackets are designed to keep the animal in a horizontal swimming position. The UnderDOG is different. By moving 90% of the effective buoyancy under the chest and neck, the vest is designed to allow a more natural swim angle with the hind legs lower than the front.
 
Disclaimer: Even though MTI builds the UNDERDOG out of the same USCG approved materials as for humans, life jackets for animals are not subject to any regulatory standards regarding buoyancy or sizes. Since dogs come in a variety of breeds, body types and coat thicknesses, always test before use.