Cools well, but lots of water sounds

Although this a/c unit cools well, there is no water drainage system, causing lots of water buildup in the unit. I verified that I installed the a/c at an angle so the water would collect towards the back of the unit, and it still makes lots of water noise (the fan slaps against the pool of water). The manual states that the water buildup is normal on humid days, and you just have to wait for it to evaporate while the sun is out...