" 

 :::I'll toss my two cents in here. Corals have naturally occurring bacteria associated with their SML (surface mucopolysaccharide layers), which are distinct to each species. I don't know what sort of effect this has on the human body, but my guess would be that any infection would arise from the bacteria on the SML of the coral rather than from bacteria in ocean water. The bacteria can include proteobacteria (α, β, γ, δ), bacteroidetes, cyanobacteria, as well as other various bacteria. Some human pathogens are included in γ-proteobacteria: salmonella (typhoid fever), vibrio (cholera), E. coli. I don't know of any studies showing if any coral associated bacteria is harmful to humans though, so don't quote me on this. "