The swimming pool is 20 cm high? Water flowing downwards cannot be higher than the ground. The bathtub can be half a person's height.
It is not good for some people in the family to avoid water.
Bridge is not at home. It is said that when building a bridge, people need to be padded under the pier to make the bridge stable. I won't tell you this story. Where the bridge is built, it is a last resort. It shows that we have to walk an unstable road every day.