The conclusion made by a coroner is a legal one. For a suicide verdict, they need evidence to show intent, including a suicide note, texts etc that essentially ‘prove’ that death was the intention. If it looks as though it was a cry for help, that someone had done this, believing they would be found and rescued, but sadly weren’t, that’s likely to be given a verdict of misadventure.
If the death is entirely unexpected and doesn’t fit the concept of it being suicide or misadventure, it’s usually an open verdict. This can involve someone with reckless behaviour, that may be high risk, but there’s no evidence of there being suicidal ideation.
Years ago when suicide was illegal, coroners and their early incarnations, were very reluctant to impose a verdict or suicide. Those who were given a verdict of suicide, weren’t allowed to be buried in consecrated ground, life insurance and even pensions were negated etc. It was also problematic in religion terms. The families would be treated badly etc.
People can seem, evidence wise to have taken their own lives, but unless there is essentially proof of intending to die, it can still be declared to have a verdict of misadventure.