What data is missing, in your opinion? What data would make the hypothesis probable?You've presented a hypothesis that because black people have an average greater bone density, this accounts for poor swimming ability among blacks, resulting in drowning deaths.
It's an interesting idea, but you cannot provide any evidence that this is born out in reality.
You are trying to correlate an irrelevant statistic with anecdotal evidence. That never works.
You would need to correlate drowning deaths over the general population with the bone density of the individual and then look to see what percentage of drowned individuals had a higher than average bone density. If you found a correlation of bone density to drowning deaths, then you could look to see the make up of that particular segment of the population.