Everyone on the craft knew it was risky. I understand the danger of dying was mentioned three times in the contract they signed.
These people, excepting the young man, knew exactly what the dangers were, but of course believed that it wouldn't happen to them.
I wouldn't use the word 'fault' but perhaps replace it with 'responsibility'. Concerns about the craft they went underwater in were generally known, they must have known them and, yes, the father is responsible for the death of his son, for even suggesting they take such a trip together, let alone the emotional pressure of having it happen so close to Father's Day. yes, both irresponsible and unnecessary.