I love this app. I use it primarily on my apple watch. The design is sleek and user-friendly. On my iPhone 6+ the application is super engaging and fun to use.
The app adjusts how much water you need not only based on your personal physical info, but takes into consideration your locations environment. Deducts when you drink coffee or other dehydration drink options. Super useful!!
I do agree with the other two reviews, that a history of entries would be ideal. Hopefully the app creators will make an edit making history viewing and editing possible.
Over all, to have such an in depth app regarding how to properly hydrate on my apple watch is just incredible!