"The animal is drinking water."
Translation:La besto trinkas akvon.
You could also translate "is drinking" as "estas trinkanta" - so the whole thing as "La besto estas trinkanta akvon".
You could say "La besto estas trinkanta akvon", which is nearly word-for-word the English sentence: La (the) besto (animal) estas (is) trinkanta (drinking) akvon (water).
But using the present participle (trinkanta = drinking), while possible, is not as common in Esperanto.
Usually, people will use the simple present (La besto trinkas akvon), which would literally be "The animal drinks water". But while in English that usually refers to habits or repeated actions, in Esperanto it's also perfectly fine to use about a one-time action that is happening right now.
La besto trinkas akvon. is a possible sentence -- in fact, it's the version I see at the top of this sentence discussion page, which I believe means that this translation is marked as the best translation.