Okay, before I start my critique; I really love the background in this drawing, it's really pretty and the colours are nice and bright! Okie then!
First of all, the back legs. The stifle and hock look like they need to be a bit more . . . bent? I'm not quite sure how to explain it, but hopefully you can understand. But to me they just look to straight for canine legs.
I think there should be a shadow underneath him/her in the water, but then again, it depends where the source of light is coming from. The shadow could be on the grass. But I'm not sure.
Anyway! This is really beautiful!!