Hypochloric acid is a weak acid, and is harmful to (most) bacteria because it lowers the pH of the water that it is dissolved in. Your body chemistry is resistant to it because you have a cuticle and because only a small fraction of your body is in contact with it, allowing you to circulate your own pH around to parts of your body exposed to the lower pH water. That said, there are bacteria who can survive at the reduced pH that hypochloric acid can produce.

It sounds like chlorine in swimming pools, don't you think?! So it's just dilute enough to be safe for our eyes but still concentrated enough to be toxic to the tiny bacteria that are 'swimming' in it. They are so tiny that they have a huge surface-to-volume ratio, compared to our bigger cells.

Hypochlorous acid (HOCl or HClO) is a weak acid that forms when chlorine dissolves in water, and itself partially dissociates, forming hypochlorite, ClO−. HClO and ClO− are oxidizers, and the primary disinfection agents of chlorine solutions.