A dog laps water up into its mouth by flipping up the tip of its tongue to capture the water, then pulling the tongue back into its mouth. The mechanism used by dogs to lap up water is the same employed by cats, albeit in a comparatively messier manner.
Due to the large size of their mouths, dogs lack the capability to suck water into their mouths, which contributes to the water spraying as the dog drinks. This spraying is lessened by the presence of many ridges located on a dog's tongue which capture water as it is lapped up into the dog's mouth. Scientists have shown that it takes approximately three laps of the tongue to allow water to reach the dog's throat, so these ridges help to keep the water in the dog's mouth as it drinks.
Additionally, dogs have structures, called filiform papillae, on their tongues that aid in drinking. These small, conical structures are similar to those found on a cat's tongue, which are responsible for the tongue's rough texture. Although not as pronounced in dogs, as evidenced by the relative smoothness in comparison to a cat's tongue, filiform papillae aid in drinking, eating and grooming.