What is the name of the show that involves a wish granting cat with a weakness to water?
At last I found it! Actually it was not a cat, but the rest of my description fits. The name is "Please! Psammea-don" (おねがい!サミアどん Onegai! Samia-don?)


It seems that it only was broadcast in Latin America, France, Quebec and the Arab World as noted by Wikipedia and it was also never released in English, so maybe that's the reason why nobody here knew this animation.

PS: I really loved the ending