If you intake sea water relatively warm, and you release it cold, you have net energy gain, which is not against Newton's law of thermodynamic. You can use said gained energy do desalinate sea water.

Just salty warm water in, cold sweet water out.

You can use this water to e.g. stop desertification of planet, because it has own energy source, so it's possible do at large scale.

You can pump water up into tower and let it down on large distance a little bit lower.

Therefore even places far from see and with bigger attitudes can get fresh desalinated water at cost of heat contained in sea water.

Where's the problem?