A few terms associated with this event catch my eye:
It seems agreed that the event was an accident, there was no intent to harm anyone, which seems entirely plausible to me. I agree that an accident can still result in criminal charges, if there was negligence involved, but in the training environment this seems potentially fuzzy.
The role of instructor seems to be pivotal to the case. If the "instructing" pilot was properly licensed in Canada as a CPL, with the required float experience, providing float flying training to a PPL+, with the goal of the candidate receiving a float endorsement from an authorized person, is within the CPL's privilege. Referring to them self as an "instructor" would be fuzzy, but giving "instruction" should not be a problem.
Was the victim also a victim of fraud? It sounds like the pilot providing instruction was flying and teaching within his privileges, so fraud is probably not an element.
The case, on the whole is alarming though, well intentioned instruction goes wrong. I think there is a big range of consideration between an accident, negligent piloting, and criminal negligence.