This　paper　presents　a　comprehensive　case　study　of　the　construction　of　a　10　km　long　large-span　underwater　tunnel　under　Taihu　Lake　using　the　cut-and-cover　method.　The　main　challenges　for　the　design　and　construction　of　the　tunnel　are　limiting　soil　deformation　and　tunnel　settlement,　controlling　the　groundwater　table,　improving　the　construction　efficiency,　and　meeting　the　environmental　requirements.　The　strategies　to　address　these　challenges　were　summarized,　including　a　four-zone　staged　excavation　configuration,　the　use　of　piles　for　tunnel　settlement　control,　and　the　use　of　cofferdams　and　waterproof　curtains　for　groundwater　control.　The　effectiveness　of　these　strategies　was　validated　by　field　observations,　including　deformations　and　stresses　of　cofferdams,　retaining　wall　deflections,　vertical　and　horizontal　ground　movements,　groundwater　table　variations,　and　tunnel　settlements.　The　observation　results　indicated　that　the　measured　values　were　smaller　than　the　design　limits,　and　no　damage　or　leakage　was　observed　during　construction.　This　case　history　provides　a　valuable　reference　for　the　design　and　construction　of　similar　tunnels.