I think I'd also want him to be seen by a dr., just for my own peace of mind. It could be they're terribly embarrassed by the whole situation; at least I'd like to give the dcm the benefit of the doubt with how she described the injury.
I'd have to 'know' the parents to determine if I thought it constituted neglect or abuse. We all do stupid thoughtless things as parents and would hate to think I'd been reported for some of the mistakes I made.
How old is this child and how did he end up sitting on this boat? Plus where was the parent at the time of the accident?? I mean, I used to sit right there beside the bathtub while my child was bathing, always.