Don't think of this as lifeguard training,but you've basically got to get them over one shoulder or under an arm, then across the torso, while using your hip and a strong kick to basically pin them against your side so they have the least possible leverage to twist around and hug/climb you. Then you have to figure out how to swim them back with one arm. Sometimes it takes a couple tries. While a passive victim is closer to death the situation is usually safer for the rescuer, especially if inexperienced or untrained.