Here’s Jesus getting baptized by John (the Baptizer, or Baptist, if you prefer).
In this video, I describe baptism as like a bath for your feelings. I know the concept of baptism is complicated, and you can also split hairs over the difference between John’s baptism and early Christian baptism. But the text is pretty clear that people wanted to be baptized after they confessed their sins. Sounds like a bath to me, and an idea that even young kids can understand.