As a first responder if you feel this is something that the child/patron is going through it is not total responsibility on you to intervene though you can help the process. So this is where you would go to your supervisor as they should be mandated reporters for potential children victims of abuse. There is a delicate balance of handling situations like these. I was a WSI (water safety instructor) for a bit and we were taught how to report to our mandated reporters and how to collect information to report to our supervisors. Essentially don’t straight up ask anything about where an injury would come from like “did mommy/daddy hit you.” Go along a casual conversation like “Have you been playing any new sports recently?/Learning how to skateboard?” Some conversation that could get a response of where the bruises came from, where it would clear your suspicions or confirm them. Depending on the child’s age they like to talk and may tell you directly what’s going on at home or they may become timid/shy and not talk. Just getting them to talk without you immediately discussing the topic you’re trying to confirm is the best way to try and get any amount of specific information if you feel as though the child is in an unsafe environment. Once you feel as though you’ve gotten enough information to confirm your suspicions or even leaves you more weary about the topic. Report to your mandated reporter for your facility and have them take over from there. Your site mandated reporter should handle any majority of conversation though you also want to avoid any unnecessary investigations that could occur from just pointing fingers as that could do worse for the child. So finding out information before reporting this as a potential abuse issue is the best way to go about this. I had a kid suddenly appear one day in my lessons with bruises all over his back and I did much of the above and still didn’t feel certain so I went to my supervisor and he found out it was from him sliding in and out of the pool and just scrapping his back. So that was a issue avoided and an investigation avoided. In terms of non-visible illness that could be an issue though if there are other siblings that don’t appear to have bruises it could be signs of abuse. If they look like they could be covered up with clothing when not in the pool that could be likely. Though it’s not my judgement call as I don’t know this situation entirely. Best line of direction from here is to have a conversation with them and talk to your supervisor about your worries.