Yikes indeed! (That's half a meter almost)
a good til I heard once was that if you are in an area threatened by flooding, put all your important documents in your dishwa and close the door. They are designed to be watertight, so even if your place floods, the documents will be dry.
Do not store your valuables or anything you would like to have intact in a dishwa thinking that dishwas are watertight. I have lived in a coastal community most of my life. And I know people who did this. To no avail. It will most definitely fill with water and possibly mud. Google search will reveal horror stories of valuables ruined by thinking this would be safe.
aquadoc has it. Please do not put important things in your dishwa for any purpose other than a good cleaning. They are not water tight in the sense of being completely waterproof. They just keep the water spraying around inside from getting out. If you drilled a hole in the top of a dishwa and filled it with water, the water would run out.
Another drawback to placing items in a dishwa is the fire hazard. I've worked several fires where people turned the water off to the dishwa thinking it would be a "safe", but the didn't unplug it. The cycle gets accidentally initialed and everything in the dishwa becomes fuel for a fire when the heating element melts the soft inner plastic of the tub.