That's obviously the way to go, but… Where does the 99% come from?

The theoretical efficiency could almost reach 1 with an infinite tube. In practice I've seen ~80%.

It sounds to me like the 'condenser' is perhaps wrapped around the water intake.

Do we want to heat up the oceans that much though?

I believe the heat is being transferred to the ocean water entering the desalination process, which reduces the energy required for desalination, so no transfer of heat to the ocean itself.