The ocean is a huge place and for you to assume that anyone would coincidentally drop a needle in neck deep water and that you would coincidentally be walking in that exact location is completely ridiculous. The ocean floor is filled with tons of seashells, some of which get broken, coarse sand, and rocks, which is common sense that most people learned as children. You have an irrational phobia of HiV for which the only solution is therapy. I suggest you seek out a therapist with whom to figure out how to overcome it.