An improved underwater breathing apparatus includes a gas- and liquid-tight helmet, with an attached air valve, tank coupling and tank bracket. The helmet further includes a flange generally conforming to the shoulders of a user, and incorporates ballast material. The air valve is attached to the helmet with the tank coupling and the tank bracket is attached to the tank coupling. When worn, the tank bracket is oriented substantially parallel to, and a finite distance away from, the user, whereby only the flange contacts the user. In other embodiments the helmet further includes an optically transparent face shield, or the entire helmet is may be manufactured from an optically transparent material. A handle may be attached to the helmet to aid in lifting and storage. The air valve may include an air flow regulator, a compressed air supply coupling or an air flow gauge.