A buoyancy lift system having an inflatable bladder with a tether stowed inside a canister secured to a vessel. A sealing member is slidably received within canister and secures to the inflatable bladder. Pressurized gas forces the sealing member and bladder outwardly of the canister. A stop prevents the sealing member from escaping the canister such that the sealing member creates a seal between itself and the canister at an outboard end of the canister. Pressurized gas is forced through a channel in the sealing member into the bladder to increase the displacement of a vessel.