Lock (water transport)

Imagine you're playing with your toy boats in your bathtub. Now imagine you have a really big toy boat that you want to bring from the bathtub to the sink. But there's one problem - the sink is too high up and the water in the bathtub is too low for the big toy boat to fit. What do you do?

You might have to use a lock! A lock is like a special elevator for boats. It's a big, enclosed area with gates at either end. When a boat wants to go through the lock, it enters the enclosed area and the gates are closed behind it. Then, the lock starts filling up with water (just like your bathtub starts filling up when you turn on the water). The water raises the boat up to the level of the sink. Once the water is high enough, the gate at the other end of the lock is opened and the boat can sail out at the higher level.

But how does the water get back down to the lower level of the bathtub? The lock has a special system of valves that can let the water out slowly, so the boat doesn't get jostled around. And then, the process can start all over again in reverse if the boat wants to go back to the bathtub.

So, a lock is a special kind of elevator for boats that helps them move up and down between different levels of water. It's like magic for toy boats come to life!