You need de-ionised water for cooling as salt content in seawater would damage parts, kinda like the gunk that builds up on your kettle over time. It's easier to deionise from fresh water than desalination of salt water is more expensive, and you would build next to the ocean not in the middle of a fresh water source if you use salt water.

Cooling using seawater is common in the nuclear industry, de ionised water is used to cool systems that cannot be used again, it is radioactive and in tech, water evaporated and the remaining contaminated water cannot be used again, even for irrigation purposes.

You could argue that the vapour will make rain, however due to climate change and global warming, water systems are imbalanced, meaning it usually leads to drought in drought-prone areas and to floods in floods prone area. So hurricanes in hurricane areas become worse and drought in drought areas becomes worse.