Yup. From a legal perspective, did a crime occur? Is there sufficient evidence to obtain a conviction? If so, what should be the charge?
This one is not clear cut. I know nothing about Caymanian law, but since it is a common law jurisdiction, there might be similarities with the situation in Canada.
In Canada, drunk driving is criminal. And so is dangerous driving and criminal negligence. These charges are included in the Criminal Code, which is federal. Drunk driving a boat is included in this category. Without going into specifics, criminal cases are decided on a standard of "beyond a reasonable doubt", so it is a high threshold. This would mean they need to gather sufficient evidence to charge.
We also have other charges called careless driving and careless driving causing bodily harm or death. These charges are under the Highway Traffic Act, which is quasi-criminal and provincial (Ontario). I don't think boating incidents are included here.
And then there are boating laws and regulations, which I suspect may apply here, if the incident had happened in Canada.
I'm not a criminal lawyer, and the above is just a bit of info to illustrate that charging someone for an incident like this is not always black and white.
Who knows why it is taking them so long to come to a conclusion. It could mean anything. It could also mean they're just on island time.