I think the problem is that there is so little contrast that the horizon is almost invisible. The second one looks better because the wood provides a little contrast, but it's not enough. IMO there needs to be some contrast between the water and sky and/or something to give the horizon some defintion, but the overall composition looks good to me (although the first one looks a tad tilted). Maybe a little post processing would fix them right up. I can't really say because I can't photoshop to save my life.
Just my opinion and you should probably take it with a grain of salt because I'm a total new to photography as it is.