One could cool temperatures down near the sea by using floating mist spray pumps to generate fine spray or mist (could be driven by wave motion). More evaporation occurs and the area cools down and along with this comes humidification of the air. With humid air more clouds are likely to form and the more moist the air the lower are the cloud bases. Low clouds in low latitudes are said to cool Earth. Clouds can reduce solar radiation to the ground by more than half, thus reducing temperatures close to the ground.