A personal flotation device includes a hard outer shell, a seat, a centered leg straddle support, and a water ballast valve. The flotation device is fully submersible and has adjustable buoyancy that allows the user to sit upright on the device, floating at approximately armpit level in the water with the user's arms free and feet dangling down. The user can use his or her arms and legs to propel through the water, or perform other activities while floating because his or her hands are free to do so.