What if fish get sucked into the pipe, too?

That won't happen when the water is slowed down.
If this is done, fish can swim away or hang around since food will come to them.

step one

get some

seawater

In the business, this is called the intake. An underwater pipe is extended from a desalination plant out into the ocean where it draws seawater, or salt water, into the system. You won't see the pipe because it's under the water. Sometimes, it's even buried under the sea bed. But sea life around the intake pipe is safe and the ocean won't miss the water.