Establishing cause isn't enough; preventing reoccurrence is why we investigate incidents and accidents. Internal investigations can sometimes, like an audit, unfortunately be akin to "marking your own homework". People who are overly invested may not draw the same conclusions that independent investigators can.
"Hindsight bias remains the primary obstacle to accident investigations" Cook, R. (1989) GAPS Centre
What does this mean in practical terms?
It means that it's very easy to sit in an office and deliberate over an incident that occurred elsewhere. Pointing out the errors that were made and referencing regulations that took the investigator hours to research won't really help anyone in the long run.
Instead, when conducting an investigation, in order to really understand the causes (it's rarely singular) one must put themselves in the shoes of those involved with the occurrence.
Instead of merely citing "lack of attention", try and understand what distractions may have been present at the time.
Instead of claiming that "correct PPE wasn't worn" consider the type, size and quality of the PPE. Does it fit well? Is it comfortable to wear? Does wearing the PPE restrict a worker's ability to perform part of the task?
When listing the arbitrary policies that weren't followed; think "does this policy actually bring any real value to the operation?".
Only when the investigation of accidents, incidents and near misses are approached holistically and with the correct attitude will the likelihood of reoccurrence really start to reduce.
Whether it's a Nautical, Technical or Workplace incident/accident we can investigate to establish contributing as well as root cause and, more importantly, provide comprehensive corrective action (for every level of cause) in order to mitigate the chance of it, or similar reoccurrences.
We have both Nautical and Technical team members who have served as Safety Officers onboard various vessel types.