There are many terrible examples of a person coming to the rescue of a drowning victim only to drown themselves. It's so common that there's a name for it — aquatic victim instead of rescuer syndrome, or AVIR syndrome. But there are many reasons rescuers can drown while many of the people they rescue survive.
Drowning victims, especially adults, can be dangerous. Someone who is panicking will instinctively clutch at anything and use it push themselves up. This means pushing their rescuer down, which is easy to do if the rescuer is tired, or if they've pinned their rescuer's arms. If you witness someone drowning, most emergency responders agree that what you need to do is look around for something buoyant before you even get in the water, get in a boat, or try to throw the drowning person something from shore. Swimming to someone who's drowning and trying to take hold of them is dangerous even for professionals. There's a reason why lifeguards carry those orange plastic buoys, and it's not their need to accessorize. Throwing a drowning person something to keep them afloat, so they don't hang on you, is essential.
But why do so many victims make it back to shore, when their rescuers die? One way to make sense of the situation is to look at the environmental factors that cause people to drown. Riptides are dangerous currents that drag people away from shore, but an oceanography professor has found out that riptides don't go only one way. Using GPS devices, he's tracked them, and found that they circulate, coming back towards land. The accepted wisdom on what to do if you're caught in a riptide is swim parallel to the shore to get away from the current, but professor Jamie MacMahan calculated that that gives you a good chance of being swept out to sea. Treading water for a three-and-a-half minutes yields a 90% chance of being brought back to shore.
Many rescuers aren't strong swimmers themselves, and keeping both themselves and a panicky second person afloat could exhaust them until they go under. By that time, the person they're rescuing is swept back to shore again.
Image: Vix B.