In this area, they desalinate seawater to make it drinkable.

Whenever he fails, he always sulks.

I bought a new bathing suit.

I bought a new swim cap.

My hobby is breeding saltwater fish.

I forgot my swimming trunks and couldn't swim.

He thinks that war is a necessary evil.

Do you understand the necessity of this project?

That information is unnecessary.

That information is completely unnecessary.