Fluorine reacts vigorously with water and oxidises water tooxygen. $2\mathrm{H_2O} + 2\mathrm{F_2} \rightarrow 4\mathrm{HF} + \mathrm{O_2}$ Chlorine dissolves in water to form chlorine water. It slowly reacts withthe water to form a mixture of hydrochloric acid and hypochlorous acid. $\mathrm{H_2O} + \mathrm{Cl_2} \rightarrow \mathrm{HCl} + \mathrm{HOCl}$ Hypochlorous acid is very unstable. In presence of sunlight, it decomposesto give HCl and nascent oxygen.$\mathrm{HOCl} \xrightarrow{h\nu} \mathrm{HCl} + \mathrm{O}$This oxygen is responsible for oxidising and bleaching properties ofchlorine.