Dragon Water Trough

The Dragon Water Trough is a trough create by Hiccup to provide dragons with water to drink.

Function
The Dragon Water Trough is a rectangular wooden box with an open top. This box can be filled with water to allow dragons to drink from it.

School of Dragons
When Astrid discovered that a Deadly Nadder had become sick upon drinking the water in the lake on School of Dragons Island, she asked the player to help the dragon as well as thirsty dragons in the future by asking Hiccup to build a Water Filter. Once this is done, Astrid fills a Dragon Water Trough with the filtered water and has the Deadly Nadder drink from it, restoring it back to health.

Trivia

 * It is unknown if similar troughs are used to feed and give water to Berk's animals, but it is very likely.