The cenote is lovely--large and inviting, as many have said. The admission price is higher than…read moreaverage, but they don't charge for life jackets, lockers, or the zip lines, unlike other places. The bathrooms and changing rooms are clean and modern. It's a mostly covered, underground cenote, which means the water is a bit cold, so keep that in mind. It's not the "best cenote in Vallodalid," but it's an enjoyable experience. Get there before the midday busses start pulling in, discharging scores at a time--it can get very noisy inside.
So why two stars? Because we made the mistake of going for the lunch buffet/cenote visit combination, which cost an astounding 1100 pesos for two. We had paid slightly less for a great dinner and cenote swim the evening before at Zazil Tunich, which might real be the best cenote in Valladolid, so were shocked by the truly dreadful, cafeteria-style food at Chukum.
Everything had been blanded down -- apparently for presumed American or European tastes -- and was tasteless, overcooked, and under-spiced. The food is plentiful, if that's all you care about, but you'd have to eat a lot to make it worth what they make you pay. Really, they ought to be ashamed to serve food that mediocre.
If you're in the area, you might want to experience the cenote, but eat anywhere else.