A full-face snorkel mask, comprising: a mask assembly adapted for extending peripherally in a sealing engagement with a face of a user, wherein said mask assembly has a breathing chamber; a snorkel assembly upwardly extended from said mask assembly, wherein said snorkel assembly has a fresh air intake channel for guiding fresh air into said breathing chamber and an exhaust air discharging channel communicating with said breathing chamber for discharging waste air therefrom; and a valve assembly; wherein said mask assembly further has an air intake chamber isolated from said breathing chamber and communicated with said fresh air intake channel, wherein said valve assembly comprises one or more first non-return air valves provided at said mask assembly for only allowing the fresh air at said air intake chamber from said fresh air intake channel entering to said breathing chamber and for preventing the waste air entering to said air intake chamber, wherein said fresh air intake channel and said exhaust air discharging channel are extended parallelly and upwardly, wherein said valve assembly further comprises a second non-return air valve provided at said exhaust air discharging channel for preventing the waste air at said exhaust air discharging channel being returned back to said breathing chamber and a water prevention valve provided at said snorkel assembly for preventing water entering into said fresh air intake channel and said exhaust air discharging channel when said snorkel assembly is submerged below water, wherein said snorkel assembly comprises a snorkel body with two end-to-end channels to form said fresh air intake channel and said exhaust air discharging channel respectively and two air passages (240, 250) discretely formed at a top end of said snorkel body that two top openings of said air passages (240, 250) communicate with said fresh air intake channel and said exhaust air discharging channel respectively, wherein said water prevention valve is provided at each of said air passages (240, 250). a mask assembly adapted for extending peripherally in a sealing engagement with a face of a user, wherein said mask assembly has a breathing chamber; a snorkel assembly upwardly extended from said mask assembly, wherein said snorkel assembly has a fresh air intake channel for guiding fresh air into said breathing chamber and an exhaust air discharging channel communicating with said breathing chamber for discharging waste air therefrom; and a valve assembly; wherein said mask assembly further has an air intake chamber isolated from said breathing chamber and communicated with said fresh air intake channel, wherein said valve assembly comprises one or more first non-return air valves provided at said mask assembly for only allowing the fresh air at said air intake chamber from said fresh air intake channel entering to said breathing chamber and for preventing the waste air entering to said air intake chamber, wherein said fresh air intake channel and said exhaust air discharging channel are extended parallelly and upwardly, wherein said valve assembly further comprises a second non-return air valve provided at said exhaust air discharging channel for preventing the waste air at said exhaust air discharging channel being returned back to said breathing chamber and a water prevention valve provided at said snorkel assembly for preventing water entering into said fresh air intake channel and said exhaust air discharging channel when said snorkel assembly is submerged below water, wherein said snorkel assembly comprises a snorkel body with two end-to-end channels to form said fresh air intake channel and said exhaust air discharging channel respectively and two air passages (240, 250) discretely formed at a top end of said snorkel body that two top openings of said air passages (240, 250) communicate with said fresh air intake channel and said exhaust air discharging channel respectively, wherein said water prevention valve is provided at each of said air passages (240, 250).