Deep down Jimmy felt comfortable being a diver, but today Jennifer and Carol had unsettled him with their taunts of tin man and monster man. How were they to know that that was what the kids at school had called him, he could not help walking with a limp. He decided to become the monster from the deep and donned his grandfathers old diving helmet. So of course they hid from him. He was a monster, and he knew it, Mrs Brown should not have asked him to look after her kids. His next game, well it would involve undressing.
Footnote. A child has no choice but to make judgements, but the hidden back story here is not to judge until all the facts are known. Jimmys next activity with the children is diving practice.