Nice simple, serene picture. I quite like how the sail boat is so small / insignificant and that the sail ends below the horizon. Personally I would prefer it without the clouds / mountains in the bottom left as I feel they're too small / faded to add anything to the image and they just detract from the minimalist style. I would also brighten the sky just a tad to make it pop a bit.

Personal thoughts aside, the horizon is straight, the water looks great, and the boat is nice and sharp. The sky is just a little noisy which you could easily fix by masking the sharpening.