Greg,
I don't know if you have the information you're looking for yet. From my perspective of being a trial lawyer in Michigan for 28 years, here are some things to be aware of:
As I understand it, you are looking for actual statistics on numbers of deaths and injuries associated with diving on sunken wrecks, as well as actual statistics on numbers of claims arising out of such incidents. This is going to be very difficult to come up with.
The suggestions above to check legal research databases is not going to give you the information you seek.
Westlaw, Lexis/Nexis, LoisLaw and their ilk compile information on
opinions and decisions of appellate courts. Understand what this means. Few cases end up going through the trial court level to the appeal level, not all appealed cases that go to a final decision have actual opinions written, and not all actual opinions written by appellate courts are published. By the time a case makes it to Westlaw et al. it has gone through a fine net. Counting the number of
reported cases on scuba diving incidents will not give you much information about the number of
actual incidents. The best you can get from such information is educated guesses based on reasonable backward projections of the data, and gross comparisons to other types of claims.
The state of Michigan (Supreme Court Administrator's Office) maintains statistics on types of cases filed in Michigan trial courts. This typing information comes from a case code suffix attached to the end of each case number when the case is first filed. This typing is very general however, and would not give you much information because a scuba negligence claim would be lumped in the "Other Personal Injury" or "Other Damage Suits" categories. Other states have similar systems. Searching this information is probably not productive.
Some courts have their records on file, e.g.
Oakland County, Michigan Circuit Court, but the search functions are limited. Basically it's limited to case numbers and names of parties. For the most part, you can't search the contents of the court papers to see which cases mention the word "scuba", at least not yet. There are over a hundred circuit and district courts in Michigan, and they all have separate filing systems. You'd have to check them all. Most are not on line. And that's just Michigan. And that's just lawsuits, not even claims, let alone number of incidents.
There are efforts to compile information and cases and settlements, but these mainly rely on plaintiffs' or defendants' lawyers reporting results of trials and settlements to their respective professional organizations, like MTLA or DRI. If you can get into these sources through a member, you can get a larger data set, but be aware that these sources are limited by their self-reporting nature. Lawyers go to the trouble to report their unusual results - big verdicts, big settlements, or stunning defeats. Run of the mill cases are boring, make up the vast bulk or everyone's practice, and just don't get mentioned in these sources.
Jury Verdict Research is a commercial enterprise that tries to collect information about every trial result in the country in negligence cases. There are competitors that have similar services. They have large databases with lots of information about the details of cases going back for many years, and they may be able to help you out, for a fee. But what they will give you is data on cases that went through to a jury verdict - and well over 90% of all cases are decided or settled before there is a trial.
Liability insurance companies know about their own claim experiences and spend a good deal of effort to find out the claims experience of their competitors. This is what actuaries do and how insurance companies set their rates. The insurers for PADI and other dive certification agencies would have a pretty good idea about injury and claim rates from scuba diving activities. This is where you need to go to get what you're looking for. However, I doubt that any insurance company would give you the data because it would be vital trade secret-type information. It couldn't hurt to ask though.