If you want me to be honest, it's pretty bad and snapshot-like.
Discounting any sentimental (this is a wild guess) reasons you may have for shooting this, the lack of color and general monotony of this photo is glaringly obvious. Maybe you might want to shoot a little higher and include something else next time.. Other than boring water (if only it was more colorful, or had some reflection, perhaps) and floating balls..
Besides, I note this really distracting thing at the top left corner. =/
if the subject is the reflections in the water, it can be a picture. The boat then is a supporting cast and not the main actor in the scene. But then I think the time of day was wrong and there was nothing interesting in the reflections anyway. Maybe a sunrise or sunset, or a very cloudy situation may work in such a composition. But you have to work to make to create adequate contrast to the reflections ... u need to have taken and work on such reflections to understand what I am talking about. For example see this pic of mine.
PS: I dont understand what the critics meant by "snapshot" but what I think they meant is that you were not deliberate in your composition. I do not see that it was entirely "snapshot" as it is apparent that some thoughts were put into the positioning of the elements. The shortcoming is more the selection of subject.