Caisson lock

A caisson lock is like a big water elevator for boats! Imagine you are playing with your toy boats in a swimming pool. You want to move your boats from the water level at one end to a different level at the other end. But you don't want your boats to swim all the way there through the water, you want to lift them up and move them there quickly. That's exactly what a caisson lock does!

A big strong box, called the caisson, is placed in the water in between two different levels, like a water staircase. Your boats float into the caisson when the water level inside is the same as the water level outside. Then the caisson can be lifted (or lowered) by filling it with water or letting water out, like a bathtub plug.

As the caisson box moves up or down, the water level inside changes and your boats are also lifted (or lowered) up or down along with it. Then, when the caisson reaches the other water level, your boats can float out of the caisson and continue on their journey through the water, but now on a completely different level!

This is very helpful for boats that need to move through different water levels like rivers or canals, and it's also a lot faster than swimming all the way through the water!